If you think he is flirting, he is totally doing it ! =p I mean, there are signs (sometimes subtle but in a clear way) all over the place. First thing you notice : eye contact, he stares at you and when you look at him ... ooohhh he looks in the other direction (if he is confident enough, he will hold that look and even smile! ... busted! ) If you two are having a conversation and then he uses any excuse to touch you (arms, hair, nose... ) well, it's pretty obvious, right? If you are in a group, let's say at the movies, and he does everything to remain close to you. If he is trying to make you laugh no matter what (even if he looks kind of dumb ^^) . Oh ! if he goes to pick you up and he sees your mom or any member of your family and says really loudly "HEEEELLLOOOOO!!!" with a lot of enthusiasm O.o ... hahahhahahahhahha... and so on. Believe me... if he is flirting, you will know. =D

If you are face to face with them, then the guy will smile at you/compliment you a lot, offer to get you something like a drink or a snack, lean towards you as he's talking to you, maybe touch your arm, ask for your contact details. Flirting over the net is similar but people tend to say things that they may be too shy to say face to face.Eliot has already explained flirting vs chatting.

When the man seems doesn't want to end the conversation with you and is showing signs of to be very happy (laughs very often), is a topic of conversation after another, he expresses an interest in what you do, many questions about what you like, he seems a candy around you. His eyes have an especial twinkle and follow your movements as if he wanted to record them forever.

Well, when does casual chat become flirting? That is the hard part. The thing is, you don't need to know if someone is flirting with you. Just relax and continue the conversation. Of course, you can always THINK he is flirting so to put a smile on your face. Hi hi. Now here is the $6 question. Is this answer a flirt or just a casual answer?

If it was face to face is easy to find out when someone is flirting with you. I would like to know if this situation was face to face or it happened while chatting.