IPhone 4 first charge time, how long?

Alright so I’ve had bad experiences with rechargeable batteries in the past so I want to make sure I don’t mess this one up too. What do I do as soon as I get the iPhone 4 activated in-store. Should I drain in completely then fully charge? Or charge it first then use it normally? Sorry if this seems a bit silly but I’ve heard those kinds of things before and I just want to use the battery to the fullest. Thanks in advance!