Calibrate your Macbook battery to keep it healthy

This is the proper procedure for calibrating the battery on all Macbook models.
Follow these steps to calibrate your battery:

Plug in the power adapter and charge your Macbook's battery until the light ring or LED on the power adapter plug changes to green and the on-screen meter in the menu bar indicates that the battery is completely charged.
Allow the battery to rest in this fully charged state for a minimum of two hours. You can use your computer during this time, but make sure that the adapter is plugged in.
Disconnect the power adapter with the computer still on, and start running the computer off battery power. You can use your computer during this time. When your battery gets low, you will see the low battery warning dialog on the screen.
Continue to keep your computer turned on until you see the warning that it is running on reserve power. Save all your work and close all applications now, before the computer goes to sleep. Keep the computer running until it goes into sleep mode.
Turn off the computer or allow it to sleep for five hours or more.
Connect the power adapter and leave it connected until the battery is fully charged again.

That's it! Calibrating your battery once a month will prolong its life and will give you the longest on-battery time per cycle.