Use a single mode of network - There is an option of GSM, UTMS or Dual mode of networking when you go to Tools > Settings > Network settings. You should select any one network, not the dual mode of networking, as you are already using a GSM SIM and need just that network to connect. The other modes are battery eaters, as many suggest.
Turn Offline Mode On when not using the phone - When you are in a meeting or a movie where you would not wish to accept any calls, you would normally switch off the mobile phone. Better option is to activate the Offline Mode, which you can do by hitting the "Switch Off" button once, and then selecting the offline option. In this mode, the phone is not switched off, but there is no connection with the network and so battery is fully saved.
*** It is said that when the phone is switched off and on, then the boot system consumes more battery, so its better to use the offline mode than switching it off.***
Your favorite theme? Have it in your phone memory - Only if there is some space in it. This trick also works really well, and if people have brain, they would have done this already.
A small theme that you are using in your mobile, would be there On for all the time. And for this, the mobile system has to be connected to the memory card and receiving the info about it. Why not keep it in your phone memory and keep the 2 systems(Memory card and phone system) not connected? This would save some battery for sure.
Packet Data only when needed - The packet data connection would automatically try to connect to the network and receive the packet data also when you don't need it, if you are still running with the default phone settings. Go to Settings > Connection > Packet Data connection and then select "Packet data connection when needed", and this will make the phone connect for packet data when you are browsing the web, and not always.
Decrease display backlight - Reduce the brightness of the backlight whenever you are not using it for some web type work. Don't be doing that until the low light hurts your eyes. This is not a trick, but a common tip for any mobile user, who wants to conserve some battery.
Avoid calls in low signals - When you see that the signals are too low and you still are making some calls, that would be a mistake until the call is too necessary. As a big percentage of battery is used to pull the network to a maximum to make the call better, and the battery drains faster.
