I find in my house, I have a hard time getting 3G signal so I keep wifi on so the phone isn't constantly searching for signal. This helps the battery life a lot. If your phone is constantly switching 3G/1X then it will drain the battery. Also I turn off bluetooth when not in the car, this saves battery life too.
Obviously if you are playing games (angry birds) or streaming video your battery will drain fast.
p.s. Make sure you have that last OTA system upgrade that came out in November, it helped battery life a lot. The FROYO upgrade was a killer for battery life and made the phone take forever to charge, after the Nov system upgrade the battery life and charging speed are back to 2.1 level, at least for me.