I posted a thread asking similar questions a few weeks back but didn't get any solid replies. How do I flirt? I'm aware I have to be subtle because straights may become angry. When I assume I was straight, I wasn't very good at flirting with girls either... I'm just somewhat lost as to how it even works. Tips?
How about making compliments on fashion? It's a safe aspect to compliment because, most people take pride in how they dress and they like when others notice. You can gauge their reaction to see if they are sending out any signals. I hope that helps.
Depends on how homophobic or open they are. If they're not homophobic but resist flirting, I'd keep it to a minimum. If they're alright with it, go wild. Wink, let your hand touch his accidentally and laugh it off with him if he does, look into his eyes and stare, so sort of flirting but playing it off as a joke if he reacts like that. It all depends. You know him better than us.
You might have a look at this, if you haven't already: http://emptyclosets.com/forum/sexual-romantic-orientation/146045-flirting.html#6