Guys, if a girl winks at you, do you think she's interested?

I'm interested in a guy I often talk to on the train. I think he's interested in me (smiles, laughs at my jokes, some prolonged eye contact, etc.), but I don't know if he intends to act on that interest or not. Based on what I know about him, he could be waiting for a clear signal from me, so I want to show him my interest, without letting all the other passengers know (I'm a bit shy), and see what kind of response I get.

What do you think, would a wink be good (and is it something you find attractive)? If you're friendly with a girl and she winks at you, do you automatically think she is interested? If you're not interested in her, do you just think it's weird/creepy?

Any other suggestions?