Restart

Restart. Try restarting your iPhone but if your iPhone is locked up or an application was frozen, you need to cancel the frozen application first before you can restart. To cancel the frozen app, press the home button and hold for about 6 seconds. You should be able to cancel the program that is locked up. Then restart your iPhone. To do this hold the sleep/wake button and wait for a red colored slider to appear. Slide your finger across the slider to turn off your iPhone. Before you turn it back on, wait for at least 10 seconds. To turn your iPhone on, hold the sleep/wake button until you see the Apple logo.

If recharging or restarting your iPhone doesn't solve your problem try another solution.

Reset. To do this, hold the sleep/wake button and Home buttons simultaneously for a few seconds. The display will quickly wipe itself and you should see the black background and white Apple logo. Just ignore any other symbols that may appear. It is important that you wait for the Apple Logo before releasing the two buttons. The Apple logo signifies that a reset is well done.

But then again, if recharging or restarting or resetting your iPhone doesn't solve the problem, you may also try another way.

Remove. More often than not, your iPhone will not work as you expect, if there is content that is not properly synced. This will require more than a restart... you may need to totally remove the problematic content. You may try to remove certain content such as contacts, calendars, songs, photos, videos, or podcasts. Such content may be causing your iPhone not to sync properly. To do this, connect your iPhone to your computer and go to the iTunes site. Change your sync options for each of the following categories: contacts, podcasts, calendars, etc. Click on the iPhone in the Source list, then select each tab to change what content is synced, and then click apply.

But if recharging,restarting, resetting or removing content from your iPhone still doesn't solve the problem, try another one.