How to Reboot the System

In the event your Android apps freeze or the system becomes unresponsive, you can try to reboot the system as follows:

1. Press and hold the Power button of your device until a pop-up menu appears. Select 'Power off' and tap 'OK' to confirm. The system will then turn off.
2. Turn the system on by pressing and holding the Power button until the Google logo appears.

How to Get Android User Guide

In addition to these tips and tricks covering some quick and easy points, if you wish to read a full user guide on Android 4.0 for Galaxy Nexus and earlier versions of the Android system, you can check out the official Android OS Help here.