Yes, as perception has commented, keep eye contact and acknowledge his presence. DO NOT look away or down but don't stare either.
A person's body language and facial expressions will change before an attack (hey, I've been in fights before
) and if you learn how to read the body and face then you have the advantage to act (and the time) if something does go down (maybe not all the time but it's a good thing to learn).
Also, start doing a slight veering of your direction, you will pick up if he (or she, lets be gender nutrel(sp) here) starts to do the same. If they do I would stop and get into a pre-attack mode (as in, get into a defensive stance (no, not that, just expect to be attacked)) and then, in a loud voice, "Hello, may I help you?". Loud enough to draw the heads of others in your direction, with maybe a quick "Sorry to yell, I'm hard of hearing" (so he/she doesn't think that you "dissed" them).
As for carrying in a "safe" neighborhood, just remember the old adage, "Bad things happen to good people". You may fall into a false sense of security just because you are in a "nice" neighborhood, and that will (can) get you killed.
Wayne