Blackberry 10 has not removable battery, so when it crash (for instance some times the touch screen just stop working), I found a way to reboot it. Just open the window and throw it away (joking... or maybe not).
Well! the way is to press all the available butons for a while:
Power + Volume Up + Volume Down + Play/Stop
Then the device turns off automatically (or you are asked to perform some action).
I was hoping that this would end with BB10. So frustrating to have my 9930 lock up just like my Tour used to. I use Quick Pull about 1 to 3 times as day. I don't hear of my other platform buddies going through this. Any end in sight?
As others have stated, just press and hold the power button to reboot.
If you have a problem with your device, log it in the issue tracker (that's what it's there for) posting here will never get the underlying issue resolved.