I suppose this is meant for the ladies, but here goes:

I've been told I'm a good-looking guy, and I'm just past 30. Not unlike a lot of men, I can be pretty shy when it comes to talking to women. I've found that it's a lot easier to approach a woman if she could tell I was checking her out, and I got something of a positive reaction from her. Sometimes though, I get a reaction that says, "Oh. My. God. Go away." I'm sure I don't have to tell you guys, that's enough to ruin my whole day. I'm not a creeper, I'm just trying to let her know that I think she's cute, and I'd like to talk to her.

I guess what I'm asking you ladies is, how can you tell if someone is checking you out or just being a creeper? And if a guy is checking you out, how would you give him the "green light" (so to speak) to walk up and say hi?