Make sure the reset button on the bottom is not popped out. If your disposal has a cord, make sure it is plugged in and there is power to the disposal. If your disposal has a cord, and there is no power to the disposal, check the breaker or GFI on the wall. If your disposer is hard wired into the wall, check the circuit breaker behind the electrical panel. If humming it is probably jammed. Use the small wrench that can with your disposal to unjam it and stop it from humming.
For any major issues with the garbage disposal, you should leave the job to a professional plumber only. Reaching your hand into the drain is dangerous, even if you believe the power is shut off. A plumber can help you evaluate the state of your disposal, and decide whether or not you need a new unit. Upgrading to a faster disposal unit with a higher horsepower can help to protect your pipes and make cleaning up after meals even easier.
To fix this problem, turn off the disposal, fill the sink halfway full with soapy water, and use a cup plunger to plunge the kitchen sink for 30 seconds to one minute. If you cleared the clog, the water in the sink should start draining at a normal pace again. If you’re still have issues, you might have to remove the P-trap under the sink to get at the clog with a snake.
3. Is my plumbing capable of handling the task? If your current plumbing frequently clogs or backs up, then you should NOT install a new garbage disposer. The additional waste that a garbage disposal creates will only increase the chances of one or both happening. Before installing a waste disposer, you’ll need to have the source of the problem identified and fixed.
STEP 1 – Many garbage disposals (a.k.a electric pigs) have a reset button located at the bottom of the unit that behaves likes a breaker switch or the reset button found on some electrical outlets. You may have to feel around for it if you can’t see it. While the disposal is off, press this button and then try to activate the disposal. If this works, skip the remaining steps and get back to doing your dishes! You solved the problem!
Make sure that there is power getting to the unit. Garbage disposals have an independent cord that is plugged into a wall socket beneath the sink. Unplug the disposal unit and plug another small appliance, like a desk fan, into the wall socket. Turn the appliance on to see if it works. If it doesn't work, check the breaker panel. If the breaker is flipped to the "On" position, there is an electrical problem on that circuit, and an electrician must be called in.
Did exactly what I expected to. We bought a house with an older disposal and the gasket/rubber that blocks things from falling down into the disposal was cut away. I replaced and is like new. It makes the disposal sound much better too. A couple things about removing disposal and installing gasket...1) use a large Allen key (short end) to stick in the eyelet to unlock the disposal. 2) the gasket fits over the mouth of the disposal and locks into place. Don't just stick the new gasket in up from the bottom hole like I did. 3) use channel locks to tighten the last bit of the disposal/sink collar by pinching the eyelet and collar screw mount. Enjoy!
If your garbage disposal is making a clicking or rattling sound, there may be some food particles that will not grind up inside. Remove power from disposer, reach into the sink hole with a pair of tongs and remove anything that is still down in the disposer. Test your disposer to be sure the noise is gone. If not continue troubleshooting your disposer issue (see below).

Garbage Disposal Replacement