Increase Smartphone's Battery Life In 11 Easy Steps

These are just some of the things I've learned while trying to get a battery backup of at least 12 hours for the past 2 years. Hope it helps! :)

1. Reduce the screen timeout time. This way, it keeps display on for a lesser time. This amounts to decent battery saving as many times your phone will receive an SMS (or a call) and you won't be able to look at it.
2. Remove the Facebook's native app. Seriously, do this. It keeps an active connection 24/7 with its server and thus takes up a lot of energy. Use mobile site instead.
3. Reduce brightness when indoors to least amount possible.
4. Switch off data network when you know you would not (or should not?) be using your phone for sometime. As a side note, if you're not using maps or geo location features, you should not have GPS mode turned on.
5. Turn off Wi-Fi if you don't have any connection or will be using the mobile data.
6. Turn off Audible touch tones, Audible selection, Haptic feedback and Screen lock sound in Settings > Sound. Unnecessary use of energy which can be avoided without any incovenience.
7. Don't let apps keep running in background. Keep shutting them down regularly.
8. Go to Settings > Applications >  Running services. Find all the apps which are running and shut the ones you don't really need. This alone can pay huge amount of dividend.
9. Regularly monitor Memory usage option present in Settings > Applications. You'll find apps which take most of your memory and energy. Remove the ones which take most amount energy and isn't proportionately useful.
10. Don't use Live wallpapers. They use energy for the whole time the phone is in on state. Use static images, ideally of smaller size. If it's 3 MB photograph, try reducing the size of photo before putting it as a wallpaper. It takes too much of memory everytime you turn on your screen.
11. Try using ringtone from the provided ones. If you use full song, it'll load the song in memory and then start playing it, which is a very costly operation. So, use tiny tones which loop within 2-3 seconds to save battery.