This is my first and hopefully not last build.
I play what i would say a VERY aggressive Xin Zhao. Players who I've come across are not taking enough chances, which ends up bad for me, cause then I'm alone.
So that's about to change, since Xin can take on 3 if not 4 champions on his very own, it all comes down to positioning.
Hope you enjoy the guide.

Pros:
Damage that is unbelievable.
Great for chasing and ganking.
Come on.. It's Xin Zhao.

Cons:
Can be squishy until mid-game, but the life steal + attack speed makes up for it.
Very very reliant on map awareness.
Counter Jungling is a b****.

I pick Smite and Ghost which is pretty much the standard summoner spells for junglers.

Smite:
Because dealing 420 damage to a creep is needed when jungling when downing a giant golem stone monster.

Ghost:
Ghost because it's great for ganking and getting out of tough situations.

Greater Mark of Desolation:
I love these runes, not only are they genius for jungling, they're also great for ganking.
Any champion would be wise to ward up every blind spot there is on the map, just to make sure they live to see the sunlight once again. Cause when i unleash fury with Xin, nothing can stand in the way of mass armor destruction.

Greater Seal of Armor:
Let me explain this in a simple way. MORE ARMOR LESS DAMAGE TAKEN. These can be replaced with dodge seals instead, but I prefer armor since I don't pick up Nimbleness in my mastery.

Greater Glyph of Scaling Magic Resist:
Once again, these are a great match with the armor seals, since when you're ganking(WHICH IS A MUST!) you can be almost 50% certain that your opponent will have atleast 1 ability that has magic damage involved. I also use Greater Glyph of Cooldown Reduction once in a while, but not often since Xin Zhao's Battle Cry (W) reduces all of your abilitys cooldowns by 1 second each hit.

Greater Quintessence of Desolation
As i said with the flat ARP marks, they are a must. If you are having trouble staying alive then Flat HP Runes are fine aswell, but I wouldn't recommend them, if you have the ARP runes.

Pretty standard mastery. Nothing special and it's actually suited for almost all AD Junglers.
What is special in my opinion is that more and more are starting to use Flash instead of ghost, which I do not prefer. I believe Flash can only be used as a defensive ability in the hands of a jungler, since Ghost has a longer duration and there for makes you a much more deadly ganker.

Right, I know what you're thinking 2 Zeals wtf? Well It's actually pretty simple, although 2 Zeals almost cost as much as a Phantom Dancer, you are still better off by buying them. Since they 2 Zeals nearly equals to 1 Phantom Dancer.
The temporary B. F. Sword is only for a smaller damage increase, and is not to be taking all that serious.
What you're suppose to take serious is that by the time you've acquired 2 Phantom Dancers, you're unstoppable. Nothing and I mean nothing would want to stand in the way of 2.5 hits per second. And more or less 60% crit chance.

The defensive item I chose is Frozen Mallet cause of it's big amount of health and it's completely insane passive effect, I mean who doesn't like a slow being brought to your opponent without pressing anything. An alternative for a team filled with AP is Banshee's Veil, which is gives great magic resistance and a nice shield similar to Morganas and Sivirs.

At the end you're usually left with a Wriggle's Lantern, which you want to trade for a Bloodthirster instead. But often the game is already won at that point.

Jungling benefits the team in a huge way, because having a jungler means that there's 3 champions which will receive "solo lane" experience, if you know what I mean.
Routine:
1: Small Golems, use Smite on 1 of them.
2: Wraiths, focus the large one first.
3: Wolfs... they can't harm you.
4: Large Golem, Smite should be ready again, but not really neccesary since you can save it for the Lizard.
5: Lizard, get dat red buff.
6: GANK! For gods sake gank everything and everyone.I start at the small golems cause I find it much smoother and quicker like that. But it still works perfectly fine.