Turn off the power for your kitchen at the fuse box. If you don't know which fuse it is, just shut off the main breaker for the house.
Make a thorough check with the flashlight of the inside of the disposal. If there are any solid objects stuck inside, like silverware or food, they may be preventing the blades from turning. Also, use the flashlight to inspect the disposal blades and make sure they aren't damaged, corroded, or missing.
Reach underneath the disposal unit. There should be a "reset" button; press it. If the button isn't on the bottom of the unit, feel around the sides for it. Turn the power back on and test the disposal.
Replace the garbage disposal with a new one. Trying to fix dull, broken, or missing blades isn't practical, and it may even cost you more than just buying another disposal.