My reply in this thread
got a little long and off-topic, so I thought I'd post the rest of it here:
If it were me I'd probably go the route of pursuing a friendship first - while making it completely obvious that I have a boyfriend and this friendship is not a secret - then flirting like mad. I wouldn't necessarily get into a deep discussion about relationships unless the conversation turned that way and wouldn't use the word polyamory at all unless until it was obvious that things were headed in the "relationship" direction (I'd use "non-exclusive" if I had to put it to words).
I hung out with lots of guys in college when I had a boyfriend (I generally find it easier to make friends with men) although I wasn't having sex with other guys at that point. Generally, I'd ask them if they wanted to join me for lunch or coffee or whatever, then I'd make a quick call to MrS and say "Hey, I won't be coming home until later, I'm having coffee with MrInteresting from English class that I was telling you about" - MrS would say "Cool, we all are going to be hanging out at the pool hall until 6 or so if you guys want to stop by." This let the guys know that there was a boyfriend in the picture and that it wasn't an issue without saying it in so many words.
Guys would occasionally ask "Doesn't your boyfriend mind that you are hanging out with another guy?" and my reply would be "Why would he? He's my boyfriend, not my owner. We don't need permission to hang out with our friends. He does worry about my safety on campus, however, so I like to let him know where I am, who I am with, and how I am planning on getting home - in case I need him to come get me. He does the same thing."
Additional details: MrS turned 21 a year and a half before me, so he and our roommates would go out to bars and whatnot - he'd tell me who all was going and which bars they thought they would go to. He'd usually check in at some point in the evening and let me know that they were all safe, if the plans had changed, and what time he thought they'd be getting home. Our roommates were gay and violence against gays was one concern - one of them had gotten beat up coming home alone one night - so we were all on board with the "traveling in groups" , "having a getting-home plan" and "running things by a non-drunk person in case this is a really bad idea" type of safety measures.