Most men will let you know they are attracted to you by looking at you, smiling at you, talking to you, going out of their way to be noticed by you. Some guys are shy, and make it a little harder to tell if they are interested, but you will still catch them looking at you, or trying to get your attention in some way.
The bigger question might be what "type" of interest they have in you, is it a sexual interest or a relationship interest. Many times guys tell us right off what that interest is, maybe not by what they say, but what they do, and we choose to ignore it. If a guy really wants to be with you beyond a sexual relationship, a lot of times he will make that clear by his actions. By being attentive, calling when he says he'll call, being where he says he'll be, generally keeping his word and being upfront with you about things. He won't be pushy about sex or intimacy, and he'll care about what you think, feel, and do.
I hope this helps. I welcome your thoughts, if you would like to talk more, please click reply.