Nothing. Use it and charge it when it gets low. There aren't any "tricks" to ensuring a healthy battery anymore, but Apple does recommend the following:
Be sure to fully charge your portable when you plug it in for the
first time, and then run Software Update to ensure you have the latest
The new Apple notebooks (2009 and up) monitor the health of your battery and charge it accordingly, so there is very little maintenance required anymore. In fact, they no longer even require battery calibrations. All new Apple notebook batteries are pre-calibrated and ready to use.
As for usage trends to ensure longevity, that too is all handled by the OS and you can consult Apple's battery article for more details.
To be honest, storing the battery in the fridge or freezer, running it down and then charging it, pulling it out when using AC, or all the other myriad of "tricks" you'll read about are snake oil. Batteries have a limited life-span, and they start to deplete as soon as they are manufactured. That is the nature of batteries. Using them only exacerbates this phenomenon. There is no magic wand to turn back the hand of time.
In closing, Apple has some tips on how to maintain your notebook's battery. Just follow their recommendations, and enjoy your new computer.