This adjustment really helped my battery life.

I wish I could recall where I found it to give appropriate credit.
The only additional change I made was to select CDMA instead of CDMA Auto in step 4. Can't say that I've noticed any difference, though.
The below did help my battery. In low signal areas I use to watch my battery drain. With this change, no more vanishing battery. Overall, a definite improvement along with the other great recommendations above.
FWIW, these are the steps. I have a Sprint Hero and running Fresh 2.0d:
[FONT="]1) Go to dialer, type in *#*#4636#*#*
2) Wait for the screen to change and then select Phone Information from the choices.
3) Scroll down to Preferred Network type and change GSM Auto(PRL) to CDMA Auto (PRL)
The explanation that was given was that this is sucking battery because the phone is connected using CDMA PRL but its set to GSM so its looking for a signal via SIM, which we don't have.[/FONT]