Press and hold the Power button
Tap Restart or Reboot
If Restart is not available, tap Power off
Wait until the phone turns off
Press and hold the Power button again to turn it back on
If the screen is frozen, press and hold Power and Volume Down for 10 to 20 seconds
On some devices, press and hold Power and Volume Up instead
If the battery is removable, remove it, wait a few seconds, reinsert it, and power on the device