When you use your George Foreman grill or other products that collect grease and oil, you may feel inclined to dump it down the garbage disposal. However, you do not want to do this. Because of the consistency of grease, it will solidify after it cools. So if you pour it down your garbage disposal, it will solidify in your drain, which will clog your sink and cause products and other objects to back up. You will want to throw this junk away, or take it to a grease and oil recycling facility. Either would be better than pouring it down your garbage disposal.
Fiber is generally considered good for your body, but the same is not true when talking about your garbage disposal. Like in the body, fiber will adhere to other products, however in a garbage disposal it will cling to the other products and either stick to the walls of the drain or disposal (which will cause a blockage), or it will stick to the actual blade and damage it. Such products you want to try to avoid are egg shells, meat bones, corn cobs, flowers and seeds. These are products which will either need to be thrown away or placed on a compost pile.
Hazardous waste should never be thrown down the drain, and this includes the garbage disposal. These products include motor oil, paint and other household cleaners. These can find their way into the water supply and end up causing serious damage to the drainage system. You will need to dispose of these by contacting your local government and asking about the closest facility capable of processing such waste.