1. Disable your 3G connection. If you don’t use 3G, or you use it very rarely, go ahead and deactivate it. It will save you a lot of battery.
Menu –> Settings –> Wireless & Network –> Mobile networks –> Use Only 2G Network
2. Adjust Sync settings. Turn OFF the ones that you don’t need, and for the ones that you use, modify the sync frequency. Depending on your needs, you can set Facebook and Tweeter to 30 minutes, 1 hour, or more.
Menu –> Settings –> Accounts –> Sync
2. Use Task Killer (or similar application) to kill the applications running in background.
3. Disable Live Wallpaper. If you use live wallpapers, you should know they eat a lot of battery, and I suggest using a normal wallpaper.