As someone already said, get to know the guy. And as Matt said, you need to let him know your a car guy. Not to long ago I sold my mustang gt to a guy I knew from a local forum. And that's the only way I knew him. I wasn't really friends with him or anything, but I knew he valued the car for what it was. That means a bunch to someone who spends time modding, detailing, and/or spending countless hours on internet forums trying to learn more about their pride and joy. I don't know if this guy is like that or not, but, if he's only putting 3k on the clock a year, he's trying to keep the miles down for a reason.
There really isn't a clear cut answer for you though, you have to gauge this guy, figure out what is going to open his mind up to YOU being the next owner of his camaro. Be that a stack of cash, or shared enthusiasm, that's something you're going to have to figure out. I would suggest maybe asking to go for a ride in it with him sometime. Complement the car, and if it feels right, slide right into your interest in buying the car. And don't low ball, a lot enthusiasts don't give a rat's ass about blue book either.
