One of the many interesting tidbits in
The Gift of Fear (an interesting book, simultaneously a sensational true-crime bestseller and the words of a domain expert):
When you need help, approach someone in a crowd and ask. Don't wait for someone to approach you. The odds that the person you choose to approach is dangerous are pretty low. Whereas the odds are higher that a person who chooses you -- notices a confused person in a crowd, walks right up to them, and offers to help -- is potentially dangerous. That's the stalker strategy.
Corollary: Expect people to be very nervous when you walk up to them in public and ask if they need help. They are going to assume, with justification, that you are more likely to be stalking them than the average passerby.