i get 11+ hours with no hardship -
1. 4G, WIFI, GPS, BT, Hotspot all set at OFF with widgets. turn ON only as needed.
2. Brightness set to very low (underneath checkmark - extreme left). this is plenty bright for me.
3. No Live Wallpaper. not sure of this makes a difference but i have my own graphic anyway.
4. No Data intensive constant data hungry widgets/apps constantly running. i wiped News and Stocks and Sprint Zone. uncheck them for sync. i will get my data from the browser fresh as needed. i have no updating widgets other than 2 weather cities with the nice big beautiful HTC Clock/Weather default widget i keep with auto refresh at 1 hour. i have 2 GMail PUSH accounts that i set up and are always on.
5. Sign out of everything when done - GTalk, Qik, FB, etc. Everything! i don't use this stuff anyway. as noted before - let GTalk run in the background for PUSH Gmail but always sign out and uncheck auto sign you in.
6. Vibrate is ON for Calls and Texts. Vibrate is OFF for emails. all Haptic Feedback - Keyboard, Screen, etc. is OFF.
7. i DO NOT use a task killer or kill tasks with the Manage Applications Panel.