Using your Q ability to hop over walls is probably what makes Shaco the strongest. Midlaners generally ward the bushes on either side of the river, so Q-ing over a midlane wall to avoid those wards usually works out pretty well.
Use boxes to help in the jungle, to screw with the enemy in their jungle or to provide/prevent escape in teamfights.
Use your Shiv (E) AFTER your Q.
Shaco's ult is good for splitpushing and doing burst damage in a gank or teamfight. Only use it when pushing towers or facing an enemy champion.
Shaco's my favorite champ, but do your best to end the game early if you get fed. He can 1v1 just about anyone lategame but can only get 1, MAYBE 2 kills in teamfights before dying. He's not a great jungler to "carry" lategame.