Garbage disposal problems usually fall into a few groups. The unit hums but does not spin, which usually means it is jammed. It does nothing at all, which points to a tripped reset button, a breaker, or a failed switch. It leaks from the bottom, the sink flange, or the dishwasher connection. Or it runs but the sink drains slowly, which usually means a clog in the drain line past the disposal.
Jams are often caused by bones, fruit pits, utensils, or fibrous food like celery and onion skins. Grease and coffee grounds tend to build up in the pipe after the disposal rather than inside it.
Before calling, turn off the power at the switch and try the red reset button on the bottom of the unit. Many disposals also have a hex socket on the bottom that accepts an Allen wrench to free a jam by turning the motor by hand. Never put your hand inside the disposal.
If that does not solve it, Haygood Plumbing connects you with an independent plumber in Pasadena, CA who handles disposal repair. The plumber who takes your job will check whether the unit can be fixed or should be replaced. A leak from the body of the unit generally means replacement, while leaks at the flange or connections can often be resealed. If you are replacing, ask about horsepower and whether the unit is hardwired or plugs in.
When you call, mention the brand, roughly how old the unit is, and what it is doing. Ask the plumber whether they supply the new disposal or install one you provide.