When you're talking to a guy, how can you tell if they're flirting with you

[imported_just_dance]

or just being friendly and nice? Whenever i'm talking to a guy and it seems like they're chatting alot to me, i take it as that they're interested in me. But i've mistakenly made that assumption too many times now!! I'm sick of feeling like a fool... my most recent mistake of that is this guy i used to work with, whenever we ran into eachother we'd always say hi to eachother, and sometimes he'd be chatty with me and it seemed to me like he was interested in me.. but i recently found out that he's married!! (through looking him up on facebook..and seeing his profile pic is of his wedding day)...wow i feel like such a fool! He's probably just one of those really friendly and nice guys who is just chatty with everyone and always wants to catch up with people...but to me it seemed like the things he was saying was like he was interested. I'm so confused!!! Doubt he was interested in being friends with me.. I'm 21, and he is like early 30's atleast i think..age difference doesn't bother me, i prefer guys late 20's early 30's... anyway... i feel like a foooooool!! i know that whats meant to be will happen, and i know i'll find the right guy someday...but i don't want to keep making this mistake thinking a guy likes me and then feeling like a fool!

So tell me....... is there any way you can tell when you're talking to a guy if they're flirting with you or just being friendly and nice??