New iPhone 4S...Battery, Usage & Care

I bought a new iPhone 4S a couple of days ago. I was wondering if I should drain first its initial battery charge then charge it for 6-8 hour or is it ok if i dont drain it & just charge it when it's almost empty? And also I'm subscribed to a cellular network & is using 3G as my means of connecting to the social network, so i expect my battery life to drain much faster than expected. Any tips on how to prolong my battery life while i'm on the go? Or should I charge my phone when ever I can?

Thank you for your time & for helping me.