The screen is one of the biggest power users on the iPhone, which means you should turn your attention to display brightness first.
To get there, hit up Settings and Brightness.
The more email accounts and services you have syncing, the faster your battery life goes by.
If you have multiple email accounts on your iPhone 4S, go to Settings ; Mail, Contacts, Calendars and turn Push to Off when you don’t need the extra accounts syncing.
Check Mail Less Frequently
If you don’t need to be notified of new mail the instant it is sent, you can turn off push and set mail to check for new messages less frequently.
Head to Settings ; Mail, Contacts, Calendars and tap on Fetch New Data.
Limit Lock Screen Notifications
Another tip is to avoid lock screen notifications for apps that send a ton of notifications. Every time you get a notification for a new email, your screen will light up, using up precious battery life.
Go to Settings; Notifications. Find the app you want to limit and tap on it.
Make sure Bluetooth is Off
This is another no-brainer. Even though the iPhone 4S uses low-powered Bluetooth 4.0, leaving it on still means another radio is running. Turn it off by launching the Settings app, selecting General, and then Bluetooth.
If you are in poor coverage areas, and your phone keeps searching for service or switching between your carrier and roaming, you might be better off turning Airplane mode on. Airplane Mode Stops Calls, But Saves Battery Life.
Go to Settings ; Toggle Airplane Mode to On
Turn off Vibration
If you receive a lot of phone calls, messages or alerts, your phone’s vibrator is working overtime. If you don’t absolutely need it, you can save precious battery life by turning it off. Open up the Settings app, and select Sounds.
Auto Lock and Sleep Fast
Because the screen uses a lot of your battery life, leaving your iPhone 4S display on when you aren’t using it is leaving battery life on the table.
Set Auto-Lock to 1 Minute if possible. If you have your PassCode lock set higher, you can still access your phone without your Pass Code, but the screen will turn off and auto lock after a minute.
Go to Settings ; General ; Auto Lock and choose 1 minute.
Limit Location Services
Look for apps that are using your location without the need to do so. Apps will tap into GPS and crowdsourced WiFi to find your location.
This is essential in Maps, but there are other apps like Facebook, and others, that use your location without the need to.
Go to Settings ; Location Services
Toggle the apps you don’t want to use your location to off.
Turn off Wi-Fi
This is kind of a no brainer. Enabled Wi-Fi means another radio is running, and using battery. It’s even worse if your Wi-Fi is on when you’re not connected to a specific network and your phone is constantly searching. Turn it off by opening the Settings app, and selecting Wi-Fi.