Alternatively you could make it a contest for on-site staff to find the most violators. And then give them a prize. I used to have a boss that would randomly show up on site and tell us whoever finds the most lease violations and gives that apt the appropriate letter (1st, 2nd, 3rd warning/violation), that employee would get a portion of the fine.
Maintenance always won because they were outside more and could see trash bags by front doors/on patios, and all of the grills we didn't allow.