Apple has laid out some really good tips on the iPhone battery care:
- To disable location services, go to Settings > General > Location Services
- To fetch new data manually, from the Home screen choose Settings > Fetch New Data and tap Manually
- To increase the fetch interval, go to Settings > Fetch New Data and tap Hourly
- To turn off push mail when you don’t need it. Go to Settings > Fetch New Data and set Push to Off.
- Go to Settings > Wi-Fi and set Wi-Fi to Off.
- Go to Settings > General > Bluetooth and set Bluetooth to Off.
- Go to Settings > Brightness and drag the slider to the left
- To turn EQ off, go to Settings > iPod > EQ and tap Off.
- Settings > General > Network and set Enable 3G to Off.