This is my build for Xin Zhao. I havent completely finished it myself, because im not lvl 30 yet, but this is what i will have for Xin Zhao. The build itself may look a little weird or bizarre but it does work.

The only two Summoner Spells are Exhaust and Ghost. They both work very well together. or as a single to get you that kill or if there are too many enemies/low on health, run away faster to safety.

First get E. Than either Q or W. doesnt matter really. Than build E first, than build your Q, than Build your W lastly.
Here is what you do when going into a fight. Push Q and W at the same time. Than charge in with E. and once you have hit them into the air with the three hit combo of the talon strike, use your ulti. its very devastating.
This combo is very efficient and does take some time to get right, as usually when they see your spear light up, the enemy starts running.

The runes are pretty much as follows:
Armor Pen. for Marks
Attack Speed for Seals
Attack Damage for Glyphs
and Cooldown Reductions for Quints.

Armor Pen. obviously so you can pierce your targets armor better.
Attack Speed, because with Xin Zhao, you want attack speed and they work quite well.
To be honest, with the glyphs, i wasnt quite sure what to put. so if anyone can find a better glyph to put. let me know.
and cooldown reduction because, Xin's abilites dont have much of a cooldown as it is, so why not make the cooldowns shorter?

For my Masteries, most of the time, you look for a build to base them off of. But with Xin, i figured, i could do better than any existing masteries page that i have found. so there it is. You cause alot of damage because of what you have in the offense page and you spend less time dead, thanks to the death cooldown. Lets you kill lots of people and if you do die, you can come back fast for revenge.

as you can see, the build is quite devastating. I took the build from a friend of mine, and modified it a little. mostly to suit me more. so you begin the game with a dagger, i know it seems odd. espically since Xin isnt that fast, thats why you care for a while until about lvl 3, but ill explain later. after the dagger, go and get the beserkers greaves. than purchase the dagger again, and start killing minions for money, you need 1650 for the B.F. Sword. than after that get the black cleaver. now you have more attack damage. than start building up to two, yes count them, TWO phantom dancers. it says that equipping Xin with at least one attack speed item benefits him more than other champs, so why not double it? after the two phantom dancers, start building up for a Bloodthirster. the item will come in handy, because about this time, you should be somewhat fed. than after the bloodthirster, (if the game is still going on) get another B.F. Sword to get the Infinity Edge. Than its total domination.