Another strategy is to simply be assertive. Rather than let a creep put me on the defensive, I will pre-emptively put them on the defensive. For instance, if someone is constantly eyeballing me in a rude manner I will eventually say, "What is the problem?" or "Do you need something?" before they have a chance to confront me. Or, if some vehicle is slowing down or suspiciously circling, the second their window rolls down, I will yell "What do you want?" before they have a chance to even ask.
I don't want to interact with strangers beyond a simple "Hi," a smile, or a door being held. Anything other than this should be a dire emergency. It is invasive, rude, and annoying to be bothered by people begging for cigarettes, money, or rides for instance or even asking directions. Trying to pick someone up of course is outright disturbing to me. Adults as far as I'm concerned should basically have it together without needing my help. I generally consider anyone trying to get my attention in public who I do not know automatically suspicious. I have the right to be left alone. You do too. Enough said.