I'm not in NC, so I can't give concessions, but our rent is due on the first, and late fees apply after the fourth, so I put up brightly colored door hangers on the third.
Since all of our apartments share common hallways, everyone knows which of their neighbors didn't pay. The only way to avoid the embarrassment is to pay on time. Most of my residents seem to care what their neighbors think of them, so it does help.