These are the normal runes, build and ability order i use when playing Maokai. He tends to be strong with a good adc as he can slow and stun very well to single targets and can push a whole lane with his ultimate. He tends no to be too good when your adc is newer to the game and isn't doing the damage required to kill an enemy. In that case play defensive and use your Q to push them under tower and your W to either get behind them to do so or the stun them there for longer.
If you get over pushed early - mid game into your tower by a enemy champion with low health don't do what most people do and run around trying not to get hit, your a big, slow champion, if you do this, they will punish you for it; in stead, stun them with your W and push them away with your Q, let your tower do its thing and punish them instead of reviving a death.
In early game it can be a challenge to push as your only really damaging ability is your E when it comes from a bush, so try to not call the shots for your adc, and generally follow their lead.

If you decide to play a twisted treeline i definitely suggest playing with at least 1 friend - but its better if its 2. I normally play bot lane and if your have no jungler than spam your E in the bushes, this will deal the most damage possible and slow them so your team mate(s) can destroy them; If possible when you do this hit your W and then your Q towards your team. As its a small map ganking lanes with Maokai is no problem, you can use your ultimate through the wall to get a surprise attack and continue to stun and slow the enemy.

Q-W
Q-W-E
W-Q-E
E-W-Q
R-Q-E-W
R-E-W-Q