How to extend and maximize my iPhone battery life?

There are several things you can do to improve your iPhone's battery life. Considering the recent issues many 3GS owners are experiencing with firmware updates 3.1 and later, these tips are important to those who don't want to charge their iPhone twice a day.

1. Turn off 3G when you don't need it for data. This actually has the added benefit of improving voice call quality for some users. Settings -> General -> Network -> Enable 3G -> OFF

2. Turn off Wi-Fi when you don't need it. Settings -> General -> Network -> Wi-Fi -> OFF

3. Reduce the brightness of your iPhone screen. Keep auto-brightness ON. Settings -> Brightness -> Use the slider to reduce the brightness as low as you can. I find the slider centered under the "i" in the word Brightness as a good compromise.

4. Turn off the GPS when you don't need it. Settings -> General -> Location Services -> OFF

5. Turn off push notifications. They don't always work, anyway. Settings -> Notifications -> OFF

6. Turn off push Mail. Settings -> Mail, Contacts, Calendars ->Fetch New Data -> Push -> OFF

7. Adjust your Mail fetch frequency. Settings -> Mail, Contacts, Calendars -> Fetch New Data -> Either choose Manually or reduce your Fetch frequency to Hourly (unless you need more frequent mail action), then touch Advanced. Under Advanced you can decide for each mail account if you'd like to fetch or update manually. Manual saves battery!

7. Make sure the Auto-Lock is set to one minute. Settings -> General -> Auto-Lock -> 1 Minute

8. Turn off vibrate. Settings -> Sounds -> Vibrate -> OFF

9. Turn off the iPod equalizer. Settings -> iPod -> EQ -> OFF

10. Turn off Bluetooth when not in use. Settings -> General -> Bluetooth -> OFF