get an app killer and turn off wifi, gps etc when your not using them

 

Don't use task killers - they drain your battery even more because its disrupting how Android works, the programs you 'kill' will just be opened back up again by Android which takes up more battery juice.

To conserve battery, you can turn off Wi-Fi, GPS, turn down the brightness, turn off auto sync if not needed (Settings>Accounts & Sync>Auto Sync), background data if you don't want apps to use the internet when your not using them (Settings>Accounts & Sync>Background Data leave it on if you want push notifications like for Facebook, Twitter, GMail etc.), use Settings>About Phone>Battery Usage to check what is using your battery and uninstall/change the app settings for it, if you don't have a strong signal the phone uses up more energy trying to get a stronger signal, so if you have a weak signal, and you don't need a signal then enable airplane mode.

Hope this helps!