If you go to the Evo 4G section of these forums (not the root section, root is a subdivision within the Evo section), there is a tips and tricks section with this thread:

http://androidforums.com/evo-4g-tips-tricks/150799-battery-tweaks-htc-evo-4g.html


As far as roms go, the saying is that everyones phone is different, and you'll just have to keep trying new kernels till you find the one that works best.

 

with kernels it will always differ for people. what works for me may not work for you. so just make a nandroid backup and try a different kernel. always give it a few days before moving on to the next one.

as far as tweeks and such for battery life i would use setcpu with a screen off profile. and keep 3g off until you need it.