If you're anything like me, patience is possibly not your biggest virtue and your phone is prone to freezing at the worst possible time. Emailing someone while waiting for a meeting, to have the phone freeze or crash when they call?
This is essentially the tip, but our mobile specialists here at DG also recommend I (and anyone else) upgrade from my iPhone 4....
*for a given value of fixed
All users need to do, when the phone is unlocked, is hold down the top power button until the 'slide to power off' slider appears, and then hold down the bottom home button for five seconds