If you have just purchased your first Android smart phone, do not panic about what I am proceeding to tell you. We both know you will be on your phone for countless hours because it is such an upgrade that it is unbelievable. However, your battery will not last long. I know, tragic. Luckily, I can help you make the most of it without spending a dime.
First off, you need to limit what resources are being spent (resources being your battery).
Unknowingly, the #1 cause of short lived batteries is your brightness level.
This is when you go into Settings -> Display -> Brightness and turn off auto brightness on your phone. Then set it to a consistent setting to where you can see easily in a moderately lit room. This will undoubtedly increase your battery life tremendously. It might even benefit your eyes a little too.
Second step is to get into the habit of toggling your WiFi.
When you are out and about you do not need WiFi on. It will just spend precious resources trying to find what isn't there. Go to Settings -> Wireless & network settings and make sure it is off.
Step three is GPS. It is the same as WiFi, it's only useful while you're using it. So when you are about to use it, turn it on. And when you are done, turn it back off. Go to Settings -> Location & security settings and uncheck "Use GPS Satellite ".
WiFi and GPS can be easily maintained by the Power Control widget. To get to the widgets, long press on your background and select "Widgets". From there, locate "Power Control" and select/place it on your home screen. From left to right the toggle selections you have are: WiFi, Bluetooth, GPS, Auto sync, and Brightness control. I prefer to have all of them off, except when I need to use WiFi, Bluetooth, or GPS to make sure my battery stays alive.
The fourth step is to turn off Bluetooth, which you can do through Power Control, like I stated previously. You can also go to Settings -> Wireless & network settings and uncheck it there.
Next, download JuiceDefender off of the Android Market.
With Juice Defender, you have to power to control and limit what has access to data while your screen is off, you have the ability to restrict multiple apps from accessing the internet period, and you can customize your settings between 4 different level restrictions. Despite what I have said earlier, do not download Advanced Task Manager, as I have stated in my newest Android Advantage article update.
After that, look through your Applications and check out which ones you really need. Delete any that you don't ever use, and your battery life will also improve. (Settings -> Applications -> Manage Applications)
A major reason people's batteries die so much is Live Wallpapers. They look really cool, but since they are running 24/7, they drain your resources in a hurry. Long press your home screen and go to Wallpapers to change it.
Last but certainly not least, is rooting your phone. It is highly unrecommended by phone companies, as is voids the warranty, but it essentially modifies the Android Operating System, allowing people with significant tech know-how to customize and improve your smart phone. A rooted phone typically has no bloatware (apps that no one uses or are useless), which will improve the performance as well as battery life. They also can overclock your phone and improve the speeds of it as well.
Advantages To Rooting Android
The Android Advantage - Why Android?
UPDATED: Android Battery Life Optimization Guide
Top 10 Free Android Game Apps
What is Android?"
Top-10 App Essentials You Shouldn't be Caught Without