Turn off radio communications that you aren’t using. If you aren’t using Wi-Fi, Bluetooth, or GPS, use the Settings menu to turn them off (Note that the GPS receiver is only turned on when you’re using an application that makes use of it).
Turn down screen brightness and set a shorter screen timeout.
Turn off automatic syncing for Gmail, Calendar, Contacts, and other applications if you don’t need it.
Use the Battery saver feature (accessed in the Settings menu) to control data activity, Wi-Fi connection, Bluetooth connection, and power used for the device such as screen brightness and notification light.
Allowing other devices to use your device's hotspot connection will drain your battery more quickly.
If you accidently press the Power/Lock Key while the device is in your pocket, the screen will turn off automatically in order to save battery power.