Xin Zhao maybe isn't that strong early game, but with this build, he is one of the most strongest champion on LoL late game. He maybe is hard because he is the ff of the enemies not allowing Xin to be that strong in a short period of time, so I use Xin Zhao in mid lane, which allows him to go to late game earlier. Ok, GO!

As you can see Xin can be a carry (or often a carry) so mark and quintessence of desolation because Xin is a tank killer, so armor pene. is a good choice of runes. Seals and glyphs I use alacrity for better attack speed, which u know is used 2 kill enemies in a blink of an eye.

Masteries, of course, is offensive for xin is a killer, offensive masteries allows him to kill enemies faster, so this is just a common sense ^_^

I start playing xin with a dagger and a hp potion, maybe the best starting build, then of course, Berserker's Greaves for movement and attack speed. Then I usually lane good, so when I return again before mid game, I already bought the Black Cleaver, which is a sweet item, giving attack damage, attack speed and armor reduction which is the best item for Xin, EVER! Then I buy Vamp. Stealer for lifesteal, together with Phantom Dancer which gives attack speed, critical chance that is very good for Xin as a killer and also, movement speed which can get you in and out of the jungle, roam around the map quickly and can also chase, escape and save a friend's life, if you get to the place quickly. Then Bloodthirster which is great for stacking life steal and attack damage, why? Because we already bought attack speed items, so now we will buy attack damage items which can be very good for the critical chance of Infinity Edge, and as I said, Infinity Edge which can give 250% critical strike, who doesn't like that? And also gives pure attack damage with some critical chance. Last item, if your enemy has a good tank, buy Last Whisper, for armor pene. but you can just substitute this with other situational items. Now with the lifesteal, attack speed, attack damage, critical chance, movement speed and whatsoever, and some tactics, you can even kill 5 enemies (with no help from ur teammates) easily. U can even play your enemies ^_^

As we all know, This is the possible skill sequence of Xin, I will just state the prior skills:

Crescent Sweep - of course an ulti, for killing tanks and whatsoever
Three Talon Strike - for better damage output and knocks enemies airborne
Battle Cry - the passive is sweet, how much more doubling it? and for cooldown reduction
Audacious Charge - just get 1 early game for initiating, chasing, slowing and others

Exhaust is key to this build. Your number one difficulty as Xin will be keeping your enemies from running so that you can unload on them. You already have a slow and a knock up, but exhaust is the icing on the cake. A lot of kills will come from chasing down enemies as they are running away. The speed you get Trinity Force, Phantom Dancer, and ghost help, but exhaust is what will make your enemy's escape downright impossible. Exhaust is also great for one on one fights with another powerful melee character. The reduced damage from the enemy can often times tip the scale in your favor. With the mastery points set as they are, you will also be reducing armor and magic resist for that extra little pow. And Ignite, ah , killing running enemies of course.

Early Game - try to lane good in mid lane
Mid Game - some ganks and kills for better money, buying items
Late Game - Don't worry, your'e that good (if you mastered Xin) and you, an IMBA!