BUT - if your lease allows it, charge residents back for repairs caused by improper disposal of grease. In my experience, the first time a resident has to pay for clearing a pipe clogged by grease, its usually the last time. I also keep flyers on "what not to flush" and "what not to put in your disposal" handy. They are included in new move-in packets, but I also give them out when we have related service requests. If the repair is minor and requires little time, the first one is a freebie and a written letter of warning is sent wit the flyer. The second call is charged back to the resident.
In the "Old Days" people used an empty coffee can. We find that because people have garbage disposals, it seems to increase the "clogged with grease" complaints.