Ad-supported apps may seem like real money-savers, but they're costing you cash by draining your smartphone's battery in a hurry. Purdue University researchers have found that free apps use up to 75% of their energy tracking your geographical location, downloading ads, and sending information about you to advertisers. Solution: Cut back on the free apps. Another tip is to load an energy-saving app like Easy Battery Saver, which has four preset power-saving modes.
If you're not afraid to flash a kernel, you can conserve battery life by underclocking your Android phone when it's idle. The process isn't all that hard to do, but it's not exactly novice-friendly either. Lifehacker has a nice overview of how to go about it.