What are some signs of a masculine man flirting?

Theres this really masculine guy whom I think is flirting with me all the time but I dont know if its just me. He seems to be always interested in what I have to say and like his attention iis fully focused on me when we talk. Also when I see him around school, he makes his way to come up to me and say Hi..btw I like him so what are some signs of flirting because I really cant tell..I suck at this lol Idk if hes just friendly or if hes gay! HELP! 10 pts best answer!