Remove as many large pieces of glass as you can with a pair of tongs or needle-nose pliers. Don't stick your hand into your garbage disposal.
Vacuum your garbage disposal with a vacuum cleaner that will suction both wet and dry material. Do this for a few minutes, until it doesn't seem like you are removing anything else from the disposal.
Press the reset button on your disposal. While running some cold water into the sink, partially cover the drain with a plate so that water can get down but objects can't come up. Turn the disposal on. The disposal will chop up very small pieces of glass and wash them down the drain. If the disposal seems to stall when you turn it on, immediately turn it back off. There may be a large piece of glass jamming the blades. Repeat Step 1 if glass remains in the disposal.
Remove your disposal from the sink and manually remove any remaining glass if you still can't clear it. This is usually easy to do, but you may need help, because disposals are heavy. Follow the removal instructions in the product manual, as different garbage disposal models will have different removal directions.