Don't use Juice Defender, or any other apps like that that attempt to save battery life by using scripts that manage your data, they'll just mess it up. Do what others have said.
Calibrate your battery properly, makes a huge difference.
Turn off autobrightness and adjust the display by holding your finger for a sec on the notification bar where you want it to be, and sliding it back and forth if you want to adjust further.
Use the power management switches in the pull-down menu and keep things off that you're not using. Basically, turn them on as needed. I keep data turned on most of the time, but if I'm in a weak area or don't plan to be using it for awhile, I'll turn it off. That will really make a difference in idle battery consumption if you won't be using it for awhile.
If you're in a non-LTE or weak LTE area, put it in CDMA only. If you have a strong local wifi connection, try using that instead. But just remember that any weak signal will drain faster than a strong one, so use whatever is strongest.
Make sure your applications aren't constantly synching. You want most things to only sync manually or when you open them, or at least have long intervals. Check the settings in each app to change this. I keep most of mine on manual sync, then use widgetsoid to force a sync of everything when I want with a single button.
Don't use widgets that update frequently or are live (moving). And don't use live wallpapers. I understand that you may wish to use these, but just realize that they do impact your battery life.
Be aware of when you're streaming or not. If you have a huge music collection on your card, don't use Pandora all the time, for instance. And be aware that many games will try to log you in to an online service even when you're just playing single player on your phone. Disable those if that's the case, or when in doubt, just turn off your data.
There are other tricks, but those are the basics. Essentially, you just get used to using your phone in a certain way that can prolong battery life. You learn what causes it to drain faster, and do those things in moderation.