'I like to have sex while dressed up as a leopard' -- perfectly normal behavior at Further Confusion, FWIW ]:-)
"Don't be creepy." is actually quite tricky. Being a person who gets interested in people and decides to approach them (with no goal in mind beyond conversation usually), I often face that "you've got 2 seconds to prove you're not a creep" glare. I usually get past that point fairly easily, but I haven't thought much about how to teach others. I think I would suggest "Have a topic to discuss" and "Break it off and GO AWAY fairly quickly." Say something appreciative or interesting to the person, enjoy a small interaction (without any suggestion of touching) and then go away. If you were at least vaguely interesting, you have built a bridge to perhaps have another conversation later. But if it's clear that you're interested in the other person more than the topic, then you're conveying that they are a target == creepy.
Obviously this will be harder if you're more interested in them than the topic, but I can't offer any suggestions there. I don't tend to find myself interested in people until long after we've discussed several interesting topics :)