boys are confusing

I dont know if im just bad at getting signals or boys are just confusing. Ive met some guys that i find attractive but im always confused in knowing if they're just being friendly or they are actually gay and flirting with me.. There have been times when boys talk to me and i just brush it off as being friendly and not until later i realize or if someone points it out to me that they were actually flirting with me. I feel like ive missed some good opportunities with some cool guys, but my obliviousness just lets me believe they're being friendly lol. So i just wanna know what are some way i can tell if a guy is actually flirting or being friendly..

like, there is this guy in one of my classes that is pretty cute. He talked to me on the first day after class and he did most of the talking because i was too nervous to say anything more haha. The next time in class there would be times that we would make eye contact. It was kinda weird because i wouldnt expect it, i only noticed because he sits in front of the teacher and i would notice he would turn and look at me and then i would panic because cute boy looking at me lol and just look down at my notes. After class i was walking to my car and he was walking next to me but i didnt notice him and he was like hey man. So we kinda talked. again he did most of the talking. but i talked more this time. I told him i was repeating the class because i didnt do good last semester and the first thing he asks was that if the girls were distracting me and i was just like "not really". Anyways he was pretty nice and cool. So im just assuming he is straight. I told my friends about it and they tell me that he could be flirting. the only thing that i makes me think that is because he went out of his way to talk to me both times, but again he could be friendly. I just dont wanna get my hopes up. I see him tomorrow and i want to try and talk to him more. Do you guys have any advice on what to say, maybe try and find out if he does like guys haha. me in particular lol. i feel like i sound like a school girl with a crush, thinking everything he does means he wants me haha. :bang: