Pros
-Best counterjungler ingame
-One of the best 1 vs 1 champs ingame
-Insane ganks
-High burst damage in mid- and lategame
-Can win games alone by pushing lanes
-Has a free ward(his boxes)
Cons
-Hard to master
-Cant defend his own jungle
-If he sucks in earlygame he will be useless in lategame
-Needs very much kills and gold for his equipment

I take armor penetration quints and marks because it wil increase your dmg outputt in mid and lategame. Armor seals will help you rushing trough the jungle without loosing too much health and in lategame you need the extra armor in 1 vs 1´s and team fights. Magic resist glyphs will help you to stay longer in fights against ap casters.

Smite is must have for every jungler. With Shaco you can easily steal buffs or make sure you get them. Also it helps you to get faster through the jungle.
Ghost is a good choise for Shaco, because ghost helps you to chase people down or run away from them. Also you can increace your distance after a Q so that enemies wont see you coming-even if they warded.

I prefer the lvl 3 doublebuff route,which starts at doublegolems and redbuff. You will end jungling after 3:30. In the video you see the old jungle but it makes only little differences Play Video

Shaco is one of the best gankers in the game. Allways say your team mates they should let the enemies push the lane so that you can gank. Allways try to gank with redbuff because it will encrease your dmgoutputt and you should try to get 2 vs 1 or 3 vs 2 situations so that you are safe. Also you should check your mana before you gank. It could be possible that the enemy jungler is counterganking you and if you cant escape you´re maybe a freekill for your enemys. Play Video

Allways jump behind your enemy with your Q,then place a Jack behind your enemy (W). After that you press R and get visible. Try to do as much dmg as you can with the crit and 2 shiv poison (E). In the best case your Enemy should get feared because of the jack and you can deal more dmg with your twin.

I hope this guide shown you how to play shaco. Go out and own them like a boss :D ahuehuehuehue :D