Tip 1: Turn off the features you aren't using.
This might be obvious to some, but this is one of the biggest causes of fast battery drain. Turn off the radio features in your phone you aren't using; even when they are idle they suck power. That means switching off the WiFi, GPS and Bluetooth when you don't need them.
Chances are you will want to keep the cellular service turned on in most situations, but if you are in an area with no service, turn it off or just put the phone in Airplane Mode. (Switching to Airplane Mode when your phone is plugged in will also make it charge twice as fast!)
Also, turn off all the apps that are using GPS or location; many of them will keep using the GPS to determine where you are and feed you information based on your location. (On the iPhone this is in the Settings menu under Location Services.)
Tip 2: Turn down the screen brightness.
The screen is the biggest power sucker on your phone. Keep the brightness low whenever you can and set the auto-lock so it turns the screen off when you aren't using it. The iPhone and Android phones also have auto-brightness settings, but you are still best keeping the screen in the 30 percent to 50 percent range if you can.
Many even say setting a darker wallpaper will save some power. And Android users, whatever you do: stay away from the live wallpapers. You are just asking for battery drain with those.
Tip 3: Kill the apps you aren't using.
How many apps do you have open on your phone right now? Go on, check. If it's more than 10 you need to heed this advice. Close apps you aren't using, or at least some of them. iOS and Android phones do a decent job of not allowing all open apps to suck your battery, but keeping more than 10 open is never a good idea. On an Android phone also kill the widgets you don't use; even if they look pretty, they are constantly updating and draining your battery.
And for those who don't know, on the iPhone, you can close apps by double-tapping the Home button to bring up the open apps. Then swipe up to remove the ones you don't need. Hit the Home button when you are done. On Android phones, you can go to the "Manage applications" area in settings or you can select the open apps menu and swipe to close the app.
Tip 4: Turn off or limit notifications.
Notifications are very useful, but they can also tax your battery. Be smart about which app notifications are enabled. Do you need notifications from your recipe app or Yelp? Also make sure those apps that are always busy -- like Twitter or Facebook -- aren't always refreshing with new updates and notifying you of them. With email, make sure you don't have notifications enabled for every new message.
Tip 5: Buy a mobile charger or battery-equipped case.
The aforementioned software adjustments will help, but they will only go so far, at least after a day of heavy use. If that extra juice doesn't go far enough, take the plunge: buy a mobile charger or case to have on hand.
There are a number of mobile chargers with Micro USB or Apple charging connectors, including the $50 PowerStick and Mophie's JuicePack Power Station.The Mophie case has another battery inside it, which makes the phone pretty chunky but also doubles your battery life.