Less Apps Less Battery Consumption:

The lower number of apps installed on your Android device the more battery you can dig out from it. This is probably the best way to save a lot of battery. Dump all unnecessary apps that you had installed once but never used them again – remove them immediately.
Installing Battery Saving Apps:

These battery saving apps have profiles or modes in which that they can toggle Wi-Fi, GPS, Mobile data, Sync etc. They automatically turns on and off such things that drains battery. You can easily find these battery saving apps on Play Store.

Use task killing apps on your android:

There are some automatic task killers and some are manual. You can even set regular task kills. The more memory you have the more fast and responsive your device would be and would save battery life.

Select 2G in Network Mode:

Go in to settings/Wireless and networks/Mobile networks/Network mode and choose GSM only in Network mode. Because in Pakistan we only have GSM  — though we are desperately waiting for 3G but until then — changing such settings would also increase battery life.

Enable Sync or Uploading Only Through Wi-Fi:

Sync files or download large files through Wi-Fi only because this way such operations will take lesser time and hence lesser battery consumption.

Here are other parts that you should keep in mind to save the battery.

Disable Wi-Fi when not needed, Disable GPS when not needed, Disable Mobile data when not needed, Delete Unnecessary Widgets, Use Lower Brightness and Screen Timeout,  and the most important thing is Keep Your Device Cool.