REduce your screen brightness…I have GPS/Bluetooth and Mobile Data switched off unless I need them, next thing I do is reduce the screen brightness to <50% and set it to auto brightness – this does seem to make a huge saving in battery life…I see a noticeable difference if I turn the brightness up to max and leave it for 3 hours.
I have the S2 and if I don’t hammer the wifi or mobile data, I can get 3 days out of it…I make calls and texts largely, check emails and web stuff if I’m bored…
Turn screen brightness down and you will extend battery life. Android apparently manages resources and background apps differently to a PC so I wouldn’t worry too much about those…switch off what you don’t need, same with the screen wallpaper – if you don’t need the interactive version, turn it off…