Turn off live wallpapers,stick to static ones,
Kill un necessary RUNNING tasks by going to Settings>Applications>Running and kill which you think is not useful.
Turn screen brightness on 40-50%.
Use Juice Defender Pro app,
Download and install Advance Task Killer,run it,uncheck the program itself from the list and hit kill. It will kill every recent app that is running.
Use keyboard without vibration and sound all the time.
Use sound for incoming texts and calls instead of vibration.
Dont full your homescreens with live widgets and dont add calender on any of your homescreens
I hope that will help.
Sent from my HTC HD2.