Normally when you first turn on a phone, you let it completely discharge (die) then charge it to full. And then normally you discharge it to a low percentage and recharge and repeat.
Some things that help with battery life: Don't let your phone get too warm during usage. Don't leave it plugged in too much after a full charge.
Other than just some good care will keep in good shape for quite some time. Good thing about the S III changeable batteries!! <3 Love that Samsung is pushing for keeping this in the leading smartphones.