Double click the home button and kill all the unnecessary apps running in the background.
I can't wait to get my 4 so I can test it's power management myself. I'm the kind of person who usually turns my brightness to the highest. Why have a Retina display when you can't enjoy it? Why stunt the features available for you? I'm gonna turn on my location services and push of Mobile Me and probably run Skype or IM in the background. Only essentials. I do hope Apple's claim of good battery life is okay. With my uses, I just hope it'll last thru my normal day before it'll dock on the charger by bedtime. I'm optimistic after reading Engadget's review of more than 2 days of normal use.