Okay, so here are a few ways that I managed to increase battery... please note that some of these methods require root (:
Turning down the brightness:
This is a no-brainer. Just go to settings and you should find it really quick. I personally keep mine about 1/4 of full brightness.
Using a dark, non-live wallpaper
I use this because I often play games on my android, so i use it to turn off wifi while doing activities that dont require it.
and my final way that requires a root...
I first made the maximum and minimum 480 mhz with "conservative" selected...
Then I created two different profiles, but only one matters for this purpose...
I created a sleep profile and set the maximum and minimum to 320 mhz and put it in "conservative" mode. this makes it so that it should last a little bit longer when not being used. I also tested it with music playing and it worked fine for that too.
As you can probably notice, i also made a profile for charging... but it just really depends if you use your phone while charging. I do so i find it helpful because it's faster at 800 mhz and it has the "performance" option selected.
Please note that SetCPU costs 2-3 dollars in the android market, and i hope you found this helpful.