Shaco is one of my favorite champions. Mainly because he can to tremendous damage and turn a tough 1v1 into and easy 2v1 (with the help of his ult).
By the way this is my first guide on mobafire, so please go easy on me.

Pros
[*] High damage
[*] Easy to learn
[*] Can clone himself due to his ultimate
[*] His boxes are like free wards!
[*] More, I'm just to lazy to list them all

Cons
[*] Squishy
[*] Targeted first
[*] Item dependent(unless you stack boxes)

Shaco does really nice damage after he gets and Infinity Edge. One of the main counters to a heavy ad champion like Shaco is thornmail. Thornmail is the reason I like having some lifesteal to replenish the hp you lose from the passive of thornmail. Also if you are having trouble with a tanky team then replace the Phantom Dancer in the item sequence with a Black Cleaver.

If you don't like the crit marks feel free to change them to armor penetration is what I would recommend.

Farming on Shaco is important, well it is important on every champion, but when I play Shaco I try to focus on last hitting until I can afford wriggles. Then I try to collect all of the jungle which will put you fairly close to a B.F. Sword. After your B.F. Sword, kills should be racking up.

If you have a beefcake (tank) on your team have them initiate. After a few seconds deceive into the fight targeting the squishiest enemy or the enemy your team has designated and get your crit preferable behind them due to Shaco's passive. Then a few basic attacks and if they are not dead throw a shiv to do extra damage. If the enemy team changes their focus to you then use your ult and continue to basic attack. If your enemy team is skilled they will notice which Shaco is real by watching if you use summoner spells or any abilities so use them all before you ult or save them to escape if you feel that you won't win the team fight.

You can ATL click to control your clone only.

BTW buffs are NOT applied to your clone. So if you have dragon buff (wolves or wraiths ect.) then they can tell which one you are.

I usually use the ward from my wriggles to ward mid if bottom lane or dragon if top lane. Try to get top lane if possible Shaco is very strong 1v1. I use my boxes to ward priority brush such as the 2 patches going into mid(red buff area) from bottom lane. If top I box the 2 patches of brush on top lane and the top tip of the brush coming from red buff to your side of the lane, above the farm of lizards/wraiths.

If you find your team getting pushed to their second turret you can throw boxes across the wall to ward the outside of your base to keep tabs on the enemy team.

I use the simple ignite/ghost combo. Ignite to help get kills early and to reduce the healing on champions like Dr. Mundo, Sion, and all of those other strong life steal/regen champions.

One thing I should mention is use ghost before deceive so that away it doesn't kick you out of stealth when you activate it. This is a great way to cover more area while invis.

I just ask that you try the build before rating.

And please any suggestions or things I may not have covered leave in comments and I will try to fix.