Maybe it's just me, but I find it a whole lot easier to do something when given a reason that seems to make sense, like this reminder on the table in the Tri-C cafeteria.
Actually, the reason given here isn't even all that compelling: "...help to keep Tri-C neat and clean..." but still it worked.
If the sign had said "Clear Your Table!" I probably would have left the trash there just to be ornery.
Kind of like the letter I got a few days ago about contributing to the college's fund-raising campaign. The soft sell approach did the job: I ended up contributing more this year than any year in the past. It seemed like the right thing to do.