One thing that I found that greatly increases the length of time my HTC Evo holds a charge is turning off the mobile network when i'm not using it (Settings<wireless & networks<uncheck mobile network). I don't use my phone really at work, and I don't have any emails that are that important that I need to have them synced even once a day, so I turn off the mobile network all together while i'm at work, and when I have break, lunch, or after work, i just turn it back on to check my emails, facebook, etc. Also, when you are at home, on campus, or anywhere where free wi fi access is available, you should use that instead of the mobile network, because, believe it or not, wi fi uses much less energy and helps your battery hold it's charge much longer than the mobile network (read this on some forum about the samsung intercept, which I had prior to the evo, and it still holds true). Along with unchecking the background data box (unless when you want to browse and purchase apps from the market), turning off gps, 4g, and location services unless you're actually using them, these are the best tricks that i've learned from trial and error to conserve battery life.