I don't know if anyone can help me with this, but how do I tell the difference between flirting and friendliness? I grew up in pretty much total social isolation from peers, so neither really ever happened, and when they happen now I can't tell which is which. Also, how do you go from talking to someone at the beginning/end of class (or other activity) to actually being the kind of friends who see each other elsewhere and do activities together?

Edit: Thank you, this is good advice. Does anyone have any advice on how to tell with women? I'm bi, and more interested in women, and they are much harder to read than men on the subject, because women's behavior with female friends is often fairly flirty to begin with.