You don't have to charge it before using it for the first time, it should already be at least partially charged.
There are some tips on this page for maximising battery life between charges e.g. less frequent email fetching, turn off location services if not needed etc : http://www.apple.com/batteries/ipad.html
That page also says :
For proper reporting of the battery’s state of charge, be sure to go through at least one charge cycle per month (charging the battery to 100% and then completely running it down).