1. Stat by holding down the Power button.
2. A small menu will appear - from it, select the Reboot option.
3. Press and hold both Volume Up and Volume Down keys while the device restarts. Release them when the device turns back on.
4. Aaaaaaand done. You're now in the safe mode. What do you do if you want to leave it?
5. Once more hold down the Power button.
6. A familiar menu will appear. From it, choose the Reboot option.
7. Yaay, your phone is restarting into normal mode. Good game.