After placing your ward and throwing out a sapling or two for vision, begin to stack your saplings in the middle of the wraith camp at 1:20. by the time they spawn, you should have 3 saplings down, enough to instantly kill the small wraiths. Simply auto attack the large one to death (not using your health pot), back to grab some pots or a pink ward, and Teleport to your tower.

Many people view Maokai as a weak laner with no damage only because he's so tanky. However, he's actually very good at trading with other champions early on due to his Q damage and his passive. Feel free to Q for farm as well as poke, especially if you've taken a mana pot or a Crystalline Flask.
Junglers love to gank Maokai because his W sets up easy kills, so make sure to tell your Jungler when your opponent is pushing up to your tower.
Maokai's W and Q also make it easy for him to make plays in other lanes early on. If you're opponent is ever gone from lane, look for potential Teleport roams in other lanes, especially bot lane where there is often a ward set up in lane for you.

Maokai is one of the strongest front line tanks in the game due to his ability to engage, peel, and soak up damage to no end. When your team is ready to fight, use your Righteous Glory to speed up and get yourself within W range of a target. At this point your team will either get a free kill from whoever you rooted, or the enemy team will turn and fight. Your ultimate makes your entire team a bit more tanky as long as you keep them inside of it, so focus on that during a clumped up fight. Also be sure to protect your carries with your Q and (when it's back up) your W. Saplings can also provide slows against diving enemy champions.