For Seniors: What to Do with a Nonresponsive iPhone 4S
If your iPhone 4S goes dead on you, it’s most likely a power issue, so the first thing to do is to plug the Dock Connector to USB Cable into the 10W USB Power Adapter, plug the 10W USB Power Adapter into a wall outlet, plug the other end of the Dock Connector to USB Cable into your iPhone, and charge the battery.
Another thing to try — if you believe that an app is hanging up the iPhone — is to press the Sleep/Wake button for a couple of seconds. Then press and hold the Home button. The app you were using should close.
You can always try the old reboot procedure, too: On the iPhone, you press the Sleep/Wake button on top until the red slider appears. Drag the slider to the right to turn off your iPhone. After a few moments, press the Sleep/Wake button to boot up the little guy again.
If the situation seems drastic and none of these ideas works, try to reset your iPhone. To do this, press the Sleep/Wake button and the Home button at the same time until the Apple logo appears onscreen.