How to Increase Your iPhone 3G Battery Life
* Turn on 3G only when you need it. I found that having 3G turned OFF saved battery life (duh!). Using EDGE actually isn’t that painful
* Turn off Location Services.
* Turn off Auto-Brightness. Manually move the slider to 25% or 33% brightness.
* Turn off WiFi until you need a hotspot. The iPhone’s WiFi will automatically try connecting to SSIDs it detects.
* Turn off Push. Change your Fetch schedule to Manually.
* Set Auto-Lock to 1 minute.
* Turn off Bluetooth.
* Limit GPS use unless you really need it.
* Do a monthly battery calibration. According to the Apple website, you should be doing this periodically. Give your iPhone a full charge, then let the battery run out. Recharge.
o Usually with lithium-ion batteries this is not necessary as they maintain no “memory effect”…but it’s worth a shot.
Hope this helps!