(This guide is under construction, and feedback would be brahsome)

First off, a lot of players will come here looking for the perfect build or the most optimal way to play a champion. The ease in Xin is that he is extremely flexible and can be built almost any way you wish. The only way in which you can build incorrectly, is by building incorrectly for the situation at hand. (Don't wear Bermuda shorts in the arctic.)

Before anything else, let's take a look at the basic meat and potatoes of Xin.

Xin Zhao is a pressure champion. A master at striking fear and respect into his opponents

Xins main strength is that he has fairly average stats across the board.

Xins main weakness is that he doesn't really excel in any particular area.

He has a knock up with Three Talon Strike.

His Battle Cry reduces cooldowns, and increases attack speed.

He has a slow, and a pursuit in one with Audacious Charge.

He can rack up his defense and dish out a massive amount of damage with his ultimate Crescent Sweep.

His passive- Challenge- allows him to drain health which not only can increase his laning strength, but can also allow him to jungle more easily, and complement a lifesteal build.

Masteries

The most important part of choosing masteries is deciding what route to take.

You could stack points into the defensive tree if you want to build a tanky Xin. More health, More armor/resists, and damage reduction.

You could also branch into utility for more mana, experience growth, and buff duration.

You could take the offensive tree and focus on bringing the most out of your damage potential

When it comes down to it. There is no right or wrong. YOU build Xin, to YOUR prefered style.

Summoner Spells

Clairvoyance, Not really the best choice. But can be handy. I'd say to leave it for other roles to pick up.

Clarity, Not recommended at all. True, Xin has mana issues. However, using Clarity as a crutch won't help you learn to conserve mana better.

Cleanse, Not too bad of a spell. Breaking CC can help you escape or bag a kill.

Exhaust, Awesome on Xin. Slowing your target to a near stop will either force them to blow their summoners, or die trying to escape.

Flash, Good at closing gaps or escaping. I'd prefer ghost myself, but to each his own.

Fortify, Keeps enemies from hitting towers. Pretty funny skill in some scenarios. I'd save it for the supports to pick up though.

Ghost, Amazing skill. Speeds you up, and has a shorter cooldown than flash. Great for both offense and defense.

Heal, Don't really need it. There are better choices.

Ignite, Good for catching stragglers. I'd still go for ghost or exhaust though.

Rally, No.

Revive, See above^

Smite, If you're jungling. You will take it. No excuses.

Teleport, This skill is actually pretty good. Covering towers, and ward ganking junglers make it really handy.

Xin's main strength is that he is a pressure champion. He excels in striking terror into his enemies. Using Audacious Charge with Three Talon Strike, he can really mess up enemies in the laning phase.

However, make sure you don't get snared or slowed while harassing with the charge. Get your opponents when they are on cooldown. Play it passive and smooth until they overstep their boundaries, and then punish them with a charge followed up by a talon strike uppercut. The key to doing this well is knowing when to commit, and when to back off. Don't aim to always kill your opponents, but aim to make them respect your strength as a lane dominator. Once you snag that key "Hook" on your audacious charge, you can feel the adrenaline flow and then decide whether to initiate and punish, or hold back and re-evaluate your risks.

I highly recommend getting a Madred's Razors early so that you can go get red buff. A Xin with red buff is quite the force to be reckoned with. I usually get my razor after I finish my zerker greaves, or when I have base shoes done (Pending mainly on how well I farm). Once you have red buff (Or your ult if you don't want to get a razor), you can go ganking and really mess people up.

Xin can mid very well also. Don't let ranged champions tell you otherwise. Xin can strike fear into mid lane, and deny them of ever farming. Xin's audacious charge gives him the range to punish people who are farming minions, or think that they can push you and get away with it. A key thing to remember against ranged mid champions, is that they usually have hefty cooldowns. You can punish them for missing an attack on you, or attacking minions with their spells. Once you initiate a strong hook on your charge, punish them. Make them fear you. Just be wary. With Xins offensive playstyle, it's easy to scare an enemy under their tower. This will make you susceptible to jungle ganks. Always be wary of the enemy jungler and ganks.

In a teamfight, you are best at coming in from a surprise angle. Flank the enemy and slow a squishy with your charge. You can also focus on picking off stragglers. Xin even has the strength to seperate the enemy force. If you can keep two ranged carries barricaded out of the team fight, then you actually are doing more damage than if you were at the team fight. Use your Ult to hit as many targets as possible, and use three talon strike to stop channeled skills (Kats Ult, Nunu's Ult, Galios Ult, etc.) and to pressure squishies to run away from you and your team.

If an enemy thinks he is slick when chasing you at a few bars of hp, and your allies are just on his heels, but he is determined to catch you... Turn around. As you turn around, hit your Q and E and punish him. It's risky... But more often than not. You can snag yourself, or your teammates a kill, and force the enemy to respect your strength as Xin Zhao. A demacian, does not retreat. So if you are chasing a Xin, remember that a good Xin, is really baiting you, not running from you.

Speaking of madreds razor. Xin is a flexible jungler as well. He's not very quick at it, but he can fight off invasions very well, and can gank efficiently. (MORE ON THIS LATER)

As I said before, Xin is the perfect warrior and can be built anyway you wish. You can build lifesteal, Attack speed, Critical, Raw Damage, even tank, and Xin will do well. Really the only area you can't tackle well is AP. As a player, your role is finding Xin's best build for the current situation.

For example, if you were going for a damage output xin and you see a Cho Gath rushing a warmogs, then your first instinct should be to build a bloodrazor to counter it.

Wriggle's Lantern (1525 Gold)
Wriggles is good if you have a razor for farming/jungling and notice the enemy has noticeably low hp champions. (This way you won't really need a madreds bloodrazor). The lanterns big pro is that it gives you a placeable ward every 3 minutes, retains the 500 damage to minions making farming easier, and has a decent 14% lifestyle to refill health after a quick skirmish. It also gives armor and damage which are (In my opinion) the icing on the cake. Amazing item on really any AD champion.
Complements: Life Steal, Map Control, Farming, Physical Defense, Physical Damage

Warmog's Armor (3000 gold)
Warmogs is a great item if the enemy team has alot of nuke damage, or if you are a prime focus in team fights. It's best taken if the enemy team has no AD champions, or if their AD champs haven't even started on a madreds bloodrazor. The earlier you grab a warmogs, the faster you can max it out. It's an amazing item on Xin, because xin can pump out a good ammount of damage early/mid game without items. That means if you are raking in some kills, or are a prime focus in fights, then this item will grant you amazing survivability. Expensive, but highly underrated.
Complements: HP Tanking, Health Regeneration

Zeal (1195 gold)
Gives Xin some attack speed, critical damage, and even movement speed. A great item if you balance it with some damage. It builds into a phantom dancer (Basically a super zeal). However, I feel that zeal is a definite milestone item and can function quite well on it's own (That is until you can afford to upgrade it). Usually I will snag a zeal, and grab a damage item to complement it (Like a B.F. sword) then finish it into a phantom dancer, or continue to work on my damage item. You could also build the Zeal into a Trinity Force.
Complements: Attack Speed, Critical, Movement Speed

Phantom Dancer (2895 Gold)
See above with zeal. Pretty much the same deal, but with a much higher bonus in all areas. Upgrade your zeal to a phantom dancer for the low low price of 1700 gold today.
Complements: Attack Speed, Critical, Movement Speed

Youmuu's Ghostblade (2272 gold)
This item... is pretty insane on Xin. Just alone it gives damage, crit chance, armor pen, and cooldown reduction. When activated though, and you go into battle cry. Xin becomes an attack speed tornado with a 50% boost to attack speed (Not including your battle cry bonus). Also it gives 20% move speed which allows you to catch almost anyone if you ghost and slow them with your audacious charge. Simply an amazing item.
Complements: Physical Damage, Critical Chance, Armor Pen, Cooldowns, Movespeed, Attack Speed

Thornmail (2000 gold)
Awesome item if they have a heavy AD carry (Really wrecks Tryndameres). It's cheap for what it does and gives alot of armor as well. Goes well with a Randuins if you really need ALOT of AD defense.
Complements: Armor (Also Counters AD)

The Bloodthirster (3200 gold)
This baby is a heavy damage beat stick. It gives lifesteal as well which is great on Xin. Especially if you already have some lifesteal or are cranking attack speed. The only issue is that it's pretty expensive. Really good if you manage to get one, even better with two or three.
Complements: Physical Damage, Lifesteal

The Black Cleaver (3065 gold)
Perfect Item for Xin. It gives a good damage boost, attack speed, and reduces a targets armor by up to 45. I'd say get this if they have alot of tanks, but hell... it'll rip even squishies apart. Get it if you like making a bloody mess of your enemies.
Complements: Physical Damage, Attack speed, Armor Reduction

Sword of the Divine (1970 gold)
The cool thing about this item is that it's active lasts for 8 seconds. Xin is a burst champion, and can blow all his cooldowns in less than 1 second. See where I'm going with this? This sword is really good on Xin because it gives a huge chunk of attack speed, and every fourth attack deals extra damage in the form of magic. He probably just duct tapes the thing to the tip of his spear. Overall, a very good item if you need some attack speed and armor pen.
Complements: Attack Speed, Magic Damage, Armor Pen

Sunfire Cape (2610 gold)
Gives health, Armor, and a aura that does quite a bit of damage at close quarters. Really good if you have chase items (Like frozen mallet), but does well on it's own because Xin can stand ontop of his target and keep them in place. Not the best item, but good if they have squishy melee carries that like to focus you. (Goes good with thornmails also)
Complements: Health Tanking, Armor Tanking, AoE magic damage aura

Stark's Fervor (2550 gold)
Gives attack speed which is always good on Xin. It also give a lifesteal aura which degrades enemy champions armor and buff's AD allies. Really good if you have some AD carries on your team and want some extra lifesteal/attack speed. It's not too expensive either.
Complements: Attack Speed, Lifesteal, Party Aura (Lifesteal), Party Aura (Enemy Armor Decay)

Spirit Visage (1550 gold)
Magic Res and some bonus health. It also reduces cooldowns and makes your health regen better. Not an impressive item byfar, but it is very cheap compared to other armors, actually goes amazing with a lifesteal build that includes a force of nature. This item also works really well if you have someone like Soraka, Karma, or Sona on your team.
Complements: Magic Tanking, Health Tanking, Cooldown Reduction, Regeneration Bonus

Randuin's Omen (2925 gold)
A very strong set of armor. It gives a nice chunk of health, armor, and health regen all in one. It gives you a alot of cooldown reduction and even slows enemys movement/attack speeds when you hit them. To top it all off, it has an activated burst ability that slows enemy champions. A really good item overall. Perfect for AD tanking, and chasing down enemies.
Complements: Health Tanking, Armor Tanking, Regeneration Bonus, Cooldown Reduction, Movement Speed Slowstrike, Attack Speed Slowstrike, CC Effect (Movement Slowdown Burst)

Quicksilver Sash (1440 gold)
It's cheap. It removes all debuffs (It even cancels Malzahar ult, Mordes ult, and ignite). It gives some magic Res, and it is commonly overlooked.
Complements: Magic Resistance, CC Defense

Last Whisper (2290 gold)
Great item for xin. Extra damage and alot of armor pen. Good for people who stack armor against you.
Complements: Physical Damage, Armor Pen

Infinity Edge (4080 gold)
The bread and butter of any critical build. While it grants alot of power, it's also very expensive. Worthwhile if you have some good attack speed items and want to balance them out with alot of damage.
Complements: Physical Damage, Critical, Critical Damage

Hexdrinker (1385 gold)
A pretty cheap item that is good to have if the enemy is heavy in AP nukes. It gives damage and magic res. also.
Complements: Physical Damage, Magic Res, AP Shield

Guardian Angel (2600 gold)
Finally we focused down Xin... Only to their horror to see him rise up from the grave and initiate another charge to a three talon stike (Hopefully picking off stragglers). A great item that adds alot of armor, some magic res, and a revival effect. Best used if team fights end up with only one person left standing. Hopefully that one person is you.
Complements: Armor Tanking, AP Tanking, Revive Effect

Frozen Mallet (3250 gold)
Sure, your audacious charge slows opponents. However, you can get some more bang for your buck with the mallets slow effect. It also gives a nice chunk of health and some physical damage. Best to get this if you need a HP boost, and have issues hunting down stragglers. Just be wary, this item is really expensive.
Complements: Health Tanking, Physical Damage, CC Effect (Slow)

Force of Nature (2175 gold)
This is an awesome piece of armor. Not only does it give solid magic res, but it also gives a very hefty health regeneration bonus. With a lifesteal build, you can literally wreck enemy teams, and go heal off of minions and be at maximum health in a few seconds. Plus it gives a decent bonus to your movespeed.
Complements: AP Tanking, Health Regen, Movement Speed

Executioner's Calling (1350 Gold)
A very weird situational item. First off, remember that this item is pretty cheap. It gives a decent buff to lifesteal and critical chance as well. However, the main reason to even consider this item is if they have a team with a strong support healer. Otherwise, it's not really as attractive. But, it's there if needed. Situational as I said.
Complements: Lifesteal, Critical, Damage over time, Decreased Healing Effects

Doran's Shield (475 Gold)
Yeah, crazy as it sounds. This item is actually pretty good as a starting item on Xin. The health regen lets him lane for a long time when paired with his passive. It gives a decent level 1 buff of 120 Health, and some armor as the icing on the cake. Good starting item, sell it later for something better.
Complements: Health Tanking, Armor, Health Regen

Banshee's Veil (2715 gold)
A nice balanced buff to Health/Mana. Some magic res, and an awesome passive to stop CC from stopping you. Really good item, especially if their team is CC heavy.
Complements: Health Tanking, Mana, AP Tanking, CC Defense

Atma's Impaler (2405 gold)
Another really bizarre situational Item. If you have alot of HP tanking ability, then this goes great with what you need. It provides addtional armor, and some critical chance. The passive makes 2% of your health added to attack damage. So 3000 health would be 60 AD. Not bad. Just beware of enemies who try to counter you with a bloodrazor.
Complements: Armor Tanking, Critical, Physical Damage

Madred's Razors (1000 gold)
Small damage and armor buff. It's selling point is its 15% chance to nuke a minion with 500 damage. Really good for jungle farming. If you get some early kills, you can pick one up to build into a bloodrazor or a wriggles. Also you can snag buffs from the jungle, and do some really nasty ganking. Amazing item that any AD champ can benefit from. Oh yeah, it's dirt cheap too.
Complements: Physical Damage, Armor Tanking, Jungling/Farming

Madred's Bloodrazor (3800 gold)
This is the item you get when a enemy has a warmogs, or really any high HP tank exists on their side. It also gives an awesome attack speed boost, attack damage, and some armor. Really good item, but really expensive.
Complements: Physical Damage, Attack Speed, Armor Tanking, Counter to HP tanks

Cheapest to Most Expensive

Doran's Shield (475 Gold)
Madred's Razors (1000 gold)
Zeal (1195 gold)
Executioner's Calling (1350 Gold)
Hexdrinker (1385 gold)
Quicksilver Sash (1440 gold)
Wriggle's Lantern (1525 Gold)
Spirit Visage (1550 gold)
Sword of the Divine (1970 gold)
Thornmail (2000 gold)
Force of Nature (2175 gold)
Youmuu's Ghostblade (2272 gold)
Last Whisper (2290 gold)
Atma's Impaler (2405 gold)
Stark's Fervor (2550 gold)
Guardian Angel (2600 gold)
Sunfire Cape (2610 gold)
Banshee's Veil (2715 gold)
Phantom Dancer (2895 Gold)
Randuin's Omen (2925 gold)
Warmog's Armor (3000 gold)
The Black Cleaver (3065 gold)
The Bloodthirster (3200 gold)
Frozen Mallet (3250 gold)
Madred's Bloodrazor (3800 gold)
Infinity Edge (4080 gold)

Early Game Items

Hexdrinker, and Quicksilver Sash both complement a heavy AP/CC team. You can snag these early as a defensive mechanism if it seems like these will be issues.

You could pick up a Zeal for some attack speed and crit chance if you are gonna lean into maybe an attack speed build with lifesteal or critical damage.

Or you could work on a Madred's Razors so that you can go farm some jungle minions/buffs. This will make you into a ganking machine also. You could top off the razor by turning it into a Wriggle's Lantern for not only the lifesteal, but also a free sight ward every 3 mins. (Best to choose Wriggle's Lantern over Madred's Bloodrazor if you see very little in HP tanking and want some extra map awareness)

You could snag a Spirit Visage also if you want a cheaper alternative to a Warmogs Armor. This is a good idea if you need some extra health. Especially if you are building lifesteal and have a strong healing support on your team.

Average Cost Items

Thornmail and Force of Nature are good options for around 2000 gold. One is great for AD heavy teams, the other gives great health regen and magic res. You should look at these two items if you are building tanky, or are getting focused down constantly for being so awesome.

Sword of the Divine is about 2k also. A great choice if you are hurting for attack speed and just grazed over the 2k gold mark. With a 60% attack speed boost, it's pretty good. Also it's active ability lowers armor for 8 seconds. It's really good for Xin to get in, do some damage, and get out.

Youmuu's Ghostblade is around 2k also. Great for attack speed, and chasing down stragglers. Everything about this sword screams Xin. in my opinion, I say get this over Sword of the Divine unless you are short on gold and divine is in your immeadiate reach.

Last Whisper is around 2k also. It gives some damage, and a hefty armor pen bonus. Really good for enemies stacking armor.

Expensive Items

The 2.5k-3k mark. These are pretty much your strong suited items. Defining in power, but you probably don't want too many of them. Xin seems to excel well with cheaper items.

Atma's Impaler is around the 2.5k mark. It's good if you are planning on snagging a Warmogs Armor. Otherwise, very situational. Building as an HP tank is nearly an all or nothing build. So be wary of their carries picking up a Madred's Bloodrazor.

Zeke's Harbinger, another 2.5k item. The ideal item for a lifesteal build. Couple this with some massive attack speed, and maybe some health tanking/health regen. Really good to consider if you have multiple AD carries on your team. (Goes real well with the active regen from Force of Nature)

Guardian Angel is 2.6k also. A good use for this item is if team fights are really close. It's costly though, so only get it if you need the extra defense. Don't be dissuaded too much by it's passive.

Sunfire Aegis is 2.6k. Expensive, but it gives alot of armor, some health, and that nifty flame aura. Recommended if they have alot of, "Get in your face" champs.

Banshee's Veil. 2.7k for this item. It's prime seller is the anti CC effect. It also gives some health and mana. Pretty costly, but if you're tired of being stun locked to death, then this item will help a ton. Synergizes well with a Quicksilver Sash.

Really Expensive Items

Now we are hitting the 3-4k mark. These items are really expensive, and you usually will only get 1-2 of them in an average game. But they really excel in granting a huge ammount of power.

Phantom Dancer, 2.9k for a super Zeal. Pretty good investment if you already have a zeal and want to upgrade it. Usually a dancer is good for late game, and needs some heavy damage items or lifesteal to bring out its maximum potential.

Randuin's Omen 3k. Man this item does ALOT of stuff. Slowdown, Armor, HP. Yeah. It's pretty awesome. Good for tower tanking as well. Best used against a team with heavy AD. The slowdown effects are the extra flavor.

Warmog's Armor 3k. Good choice early game, but expensive so it makes it a pain in the *** to get. Warmogs gives alot of health, and synergizes well with Atmas Impaler. Just watch out for Madred's Bloodrazor. It shreds warmogs to pieces. Good thing about warmogs is that Xin already has high base damage early/mid game. So you can effectively rush this item if your team needs some extra tankiness.

Black Cleaver 3k. Damage, attack speed, and armor reduction. This baby shreds enemies. Goes well with Last Whisper. Best used against heavy armor tanks, and if your team has alot of AD.

Bloodthirster 3.2k. Really expensive item, but really powerful if you can get multiples. Not really the best choice on Xin in my opinion... Unless you have some really cheap attack speed items. It's just really expensive to stack these.

Frozen Mallet 3.2k. Another really expensive item. It gives a huge chunk of health though, and a slowdown effect that really makes it difficult for enemies to escape your wrath. Probably best for catching stragglers, and if you need some extra health.

Madred's Bloodrazor 3.8k. Wooow really expensive. But man, this razors got some blades on it. Bloodrazor destroys HP tanks, and gives a massive attack speed boost. Really good item, but really expensive. If you didn't build your razor into a Wriggle's Lantern earlier, then maybe building it into this will suit your needs.

Infinity Edge 4.1k gold. Damn this is expensive. But damn is it powerful. If you get an IE, you really won't need any other items for damage. Snag a Phantom Dancer or a Youmuu's Ghostblade and you'll be a whirling tornado of critical hit death. While it grants amazing power, just make sure you don't gimp yourself on other items.

(Under construction. Heck this area may be the size of an entire guide itself when I'm done -grin-. No exception though. Xin is a decent jungler. He excels alot at invasion and ganking.)

Is there anything you would like to see added? I'm currently working on the jungling part. I plan on adding good warding locations, and each jungle route you could take (along with the clear times)

Do you think items like Trinity Force and Wit's End would work on Xin? I'm skeptical to add them, but am considering it. What do you think?

What's your favorite flavor ice cream? I prefer cookies and cream myself, but peanut butter cup is good also. Especially with hot chocolate syrup and sprinkles.