Mine is - DO NOT go to the building you work at. Like if you’re a retail worker, it is not wise to go to the store you work at or the restaurant. Because they see you come in shopping for whatever reason, they’ll possibly be on your ass about you being able to come in and shop but not work that day.
My only rule for PTO days is never forget that you put in for them and accidentally go to work. So far I have a 100% success rate in avoiding that.