well there are subtleties, like extended eye contact, how they walk. they dont have to be OMFG gay, but youll notice i slight sway in their walk, which apparently i have. and wasnt notified until the girl who sat next to me in graduation pointed it out when we were walking up for our diplomas lol.
but uhmm, sometimes you just gotta shoot and hope you strike. my gaydar has reached a point where, pretty much every guy i see looks gay in some sort of way. sometimes you can just tell, youll feel the gay energy surge inside of you, lol. but one sure fire thing, is when an attractive guy walks by them, look at their eyes, theyll almost always do a quick up and down scan of the guy, it lasts like a fraction of a second you really have to pay attention.
those are some of the ways i used to tell, we had a couple at gay and bi guys at my school, but they were either blatantly obvious, or they werent completely out. but there were A LOT of closeted individuals i could definitely tell. sucks i wasnt ballsy enough to see if they were bout that life, def couldda got more action, but im happy with 1 and a half lol. that was long af for no reason hope i helped. AND TAKE CHANCES, YOULL REGRET IF YOU DONT.