'A demacian does not retreat'...double kill...triple kill. Xin is by far my favorite champion...he hasn't been seen much until now...like master yi he is a favorite for many people. I have seen many Xins...good, bad, but through all my experience, Xin has been misused and underestimated a lot. For one, Xin is very commonly used as a tank...this is wrong in so many ways...this build is not permanent and should be adjested to fit your style. enjoy :)

I usually like to start of with boots of speed, 2 health potions and 1 mana potion. Boots of speed is a slight advantage over your oponent. It allows you to efectively chase them. After I lane I go back and get a dagger, and usually a vampiric sceptor to avoid going back to base to heal. After laning for awhile, I aquire enough money to upgrade to mercury threads. Mecury threads are extremely important, especially to Xin because of his proness to CC effects. If he is stunned, well, besides a summoner spell, Xin has really no way to escape. At this point if first blood has not been drawn yet, it is important to obtain zeal, this gives you a significant amount of critical chance, and is not only easier to last hit minions, it is also easier to get a kill. Dash in with a charge, battle cry, three talon strike, then charge again. After you get some more money get BF sword, not only does it give a nice atack damage boost, combined with the vampiric sceptor you bought earlier, it'll let you lane much longer. It'll be about mid game now, aqquire a phantom dancer, immediately following up with bloodthirster. The attack speed, damage and lifesteal, allows you to take 2 enemy champions with more ease. This is now late game, and if the game hasn't ended yet, build for a frozen mallet. The health increase allows you to take on sometimes three champions. If the game still hasn't ended, build for another bloodthirster, to add more damage to three talon strike. By now, your first move should lower squishie champions like ashe to extremely low health without ultimate. Finally, build for infinity edge, and well, your already probably beyond legendary.

Attack speed plays an extremely crucial role in early game, especially combined with vampiric sceptor to let you stay in lane longer, even without mana. Also with the quintessence of wisdom, it can be beneficial for early game to acquire your ultimate before everyone else. Also, critical chance can help in early game for 'last-hit minion'

I take 3 talon strike first, but I always make sure to tell one of my teamates to take a slow or stun move, three talon strike deals a significant amount of damage, however, if your teamates do not have a slow or stun, take your third move for the slow. After three talon strike, I usually take battle cry. Battle cry not only gives better sttack speed, but helps cooldown, which in this case is your first move. After battle cry, I finally take the third move for a better played combo. Rush in with your third move, use battle cry, and then three talon strike. Three talon strike, when used after battle cry, lowers the cooldown of your third move, to have it available before the enemy reaches turret range. At level 6, obviously, your ultimate is taken. Keep in mind your ultimate does the most damage then any other ultimate at level six, with exception of Nunu's and Veigar's. Your ultimate not only does about 300 base damage, it also does 15% of the target's health. Therefore, you must use your ultimate first, when the enemy is at full health, to do the most damage.

I take ghost and flash, because ghost is probably the best form of chasing after enemies, and flash, is a significant way of running away. (flashing through walls)
Other Alternatives:
Heal- Heal is extremely powerful early game, it will heal you and and other champion nearby. This is very effective in keeping an ally alive. However, heal may not be a good source of escaping, especially when your opponent is tank. Another disadvantage, is that it is not exactly effective in late game.
Cleanse- Although Xin has his third move for escaping, cleanse can come in handy for slows and stuns. You can take ghost and cleanse. So when someone stuns or slows you, you can easily cleanse and ghost away.
Clarify- Clarify is useful in staying in lanes to refresh your mana. Although it does refresh mana, I personally don't take clarify because mana potions are enough or sufficient to keep you in lane long enough
Never take:
Revive- Seriously? Revive? I understand that it is useful for getting revenge, but it has a 9 min. cooldown. It's just not worth it.

As I stated before, for an early game gank, one of your teamates need to have a slow or stun move, to keep someone from escaping, so that you can take your first move for the bonus damage, and if it reaches the spells end, knocks them up, and disables them. If a team fight starts, make sure to get in quick and use your ultimate, if you can hurt all enemy champions, then you have an advantage, of not only getting a few kills, but also giving your team some time to push.

I find that critical strikes are extremely useful in last hitting minions. Farm and ast hit, but be wary of your opponent's mana and health. If it is someone like master yi, harass him with your third move and first move, causing him to waste mana on meditate. If your opponent has no mana and full health, while you have full health and full mana go for him.

Many people with full offense: bloodthirster, infinity edge, loads of criticals. However, I find that those builds are not good enough. My build may not be perfect, however, it gives you some offense, and also health, to help you turret dive, to get more enemies. Some builds also give loads of attack speed to get the most out of his passive ability(heal every third hit). My build provides enough attack speed to get some out of his passive and also get a lot of the two bloodthirsters. (bloodthirster- 100 dmg. and 15% lifesteal)

If you are jungling with Xin, make sure to alert your team to help you get the blue buff before going into their seperate lanes. With a blue buff, you can jungle longer, because you have a faster mana regen, and can use moves more often. At around level 4 or 5, I suggest going for the red buff, and at level ten, go for the dragon. In the beginning, I won't suggest going for the wraths or golems, because of their lifesteal and high armor. I suggest going for the wolves first, but if you want to start off killing the golems, make sure to take three talon strike, for bonus damage. Also if you will jungle until mid game, take vampiric sceptor first, then build to a bloodthirster. After you come out from the jungle, build for berserker greaves. Then build for phantom dancer, frozen mallet, and then so on. If your team has the extra time, go for a baron kill at around lvl 13 or 14.

All in all, Xin is capable of very much especially if he is the first to get his ultimate. This build will give some offense, mana, and enough to turret dive without losing too much health. This build however, is not set in stone, and should be adjusted to your own playing style. have fun, and remember, a demacian does not retreat. :)