As a plumber, I see all kinds of things that have clogged drains.  Some of the most common things that will be sure to clog your drain and should not be either washed down the sink, even with a garbage disposal are:

Egg shells (1 or 2 are ok)

I often see people think that it’s OK to just clean out the refrigerator and instead of throwing out the contents in the garbage, they just wash it down the sink and use the garbage disposal.  My advice is to throw away what you can and only poor liquids down the drain.