If the unit hums or it tripped the reset switch, then it is probably jammed. Turn off the switch and disconnect the power again. Some disposers come with a tool and have a socket to manually crank the blade. Use the tool that came with the unit or if you do not have the original tool, an allen wrench (usually 1/4 inch).
Reach under the disposer and insert the wrench into the socket in the very center of the bottom of the disposer. Turn the wrench back and forth until you can move it freely in a complete revolution. Turn it counterclockwise to loosen a tight jam. Remove the wrench. Reach into the drain with tongs to remove whatever caused the jam. Restore the power, turn on the water tap and turn on the switch. If it is still jammed, repeat the steps above.
If your unit does not have a feature for manually clearing a jam, use a wooden broom handle. Turn off the switch, unplug the disposer and stick the broom handle into the disposer drain in the sink. Push the handle or use leverage to attempt to move the blade inside the disposer. Turn it counterclockwise. Remove the broom handle, plug in the unit and turn it on. If it is still jammed, repeat the steps above.
If your problem is a that the water drains too slowly or you have water spilling from the air gap into the sink, see our section on sinks and clogs.