1. Turn it off when not in use. There's an automatic turnoff function.
2. Remove every instant message program. The only apps that I have running on my Blackberry are Blackberry Instant Messenger (which I can't easily delete), and mail. Everything else goes. If you don't use it, get rid of it. No AIM. No Facebook. No nothin. It all sucks down battery.
Those two things get you battery life.