1. charge it fully
2. turn it on
3. discharge 'til 5-10% or whenever it goes into standby. if nothing else, this calibrates the battery power meter.
if you leave your computer plugged in at a desk for weeks at a time, use it on battery for a little while once every week or two (Apple's recommendation). if you use the battery regularly, don't worry about it.
once every couple months, discharge the battery fully to calibrate the battery meter. a "full" discharge is until the computer goes into standby, or close to it (around 5%).