You gotta be comfortable with yourself first before you become comfortable with another person.
That being said, are you looking for someone to just pop your cherry ('cause there might be some very
willing people here on RJ) or are you looking for someone special you can share that first time with?
When I became comfortable with myself, I pushed my comfort level outwards a level and joined the local gay volleyball team and various gay groups here in the South Bay and that increased my exposure. I met lots of cool bros and it just made it worth it. Plus, you learn about your potentials before you do
Your first time will be a nervous experience - you won't know what to expect. Some people pigeonhole their preference before they even get to it. I pigeonholed myself as the bottom (and sure, I've earned the title of a powerbottom), but it's not the be all and end all - you gotta learn to be flexible (no pun intended) and willing to try things out. Try to guage if the guy you're interested in is just the pump and dump type or if they're the sensual, erotic, love-making type. The latter are the best because you can feel every sensation as he's going in and out and. . .excuse me
Oh, and size doesn't matter the first time. A lot of people will tell you otherwise, but my first time involved a man who was 6-5 (and I'm only 5-4; it was like a great dane mounting a Chihuahua) with a 9 x 6 wang (I measured). That shit fucking hurt. But, luckily, he was sensual and erotic and totally made the experience worthwhile (of course where
it took place is a WHOLE 'nother story. . .). If you're the bottom, a good top will watch you and focus his attention on you. It takes a lot of trust to be a bottom and a good top knows/understands that so he shouldn't go fast until you're primed and ready. And don't forget the lube and condoms. I know it's silly to have to remind people, but speaking from experience, it's much more pleasant with them than without.