(Do not mention the forum's name, in case it counts as advertising.)
I was 9 when I joined my first forum, a Pokemon forum which I do not want to mention for fear of breaking the advertising rule.
I was 12...and i still am.
I joined the forum at that age.
And if you haven't notice. The forum i joined is the forum you guys are currently in *coughcoughacanthitecoughcough*
My first was actually a Bionicle (yes, the lego subseries) forum called MNOnline V3 which is down as of December 2008. :(
I joined it at age 9. I soon joined Bionicle Bomb forums, where I met Katamai and Chaos Kiata. They created Biofactor forums, and I became a mod there. Biofactor became Bio Zone, then bioEvolution, then finally bioCiety (which went down I don't know when). I stayed with them until I was promoted to Admin sometime during bioEvolution's closing period (I'd say February 2007). By then, I was getting out of the Bionicle craze. I left literally a week after, and bE merged with SoSiety to become bioCiety. I'd been there 2 and a half years. Last I checked it was still up, this was around January of this year actually. But it's down, I tried using the URL just now. Bionicle Bomb and the archive of Bio Zone were both cracked by some gang of losers.
There's my story (and why I had prior experience as mod). I don't think it's advertising, since none of these sites are even still up. :P
During the summer of 2001, I found a forum dedicated to playing Yu-Gi-Oh! online. I played pretty well and got whipped a couple times, but made friends with (almost) everybody. It wasn't long before I was promoted to moderator for my idea of adding an RPG element to the forum.
That was a LONG time ago and I am definitely sure it's not up anymore, but I remember the admins Hero of Time and Mystic Mage. It's just too bad that I don't have their contact information anymore. Anyways, that was my first forum, considering that's the first summer I had the computer and the internet, dial-up nonetheless :D.
Monster and Me MMO forums where I became one of the few legends in and game and forums. But then the game got riddenwith hackers, the forums were moved to a better service..which blew ass and signs me out every new page veiw, and the game got old. Im still in contact with most of the people I cared about. Many of us are good friends now :P
I'm not too sure...
I was around 10 years old when I joined Gaia Online. Played for 3 days :P
After that, I joined a few other forums and started to like it a lot. I became a 'forum-freak' :P
After a while, I found this forum and this had to be one of the forums I'm really active on (well, I think I'm active :P)
10.
I was such a noob back then. D:
13, I joined scarlet as a sorta birthday present because I am not aloud msn, twitter or facebook. So it was my first online thing. I almost noobed myself, but I got over it. Now im here.
17
Yeah, it's the site you go to if you click my trainer card. I already knew about it and thought I would join because I wanted to battle people in Diamond because I though I was really good. (I got owned a lot.) I made some friends, but after a while they stopped coming on and now I don't do too much there. Then I joined a manga forum and I don't know why. I only go there to read manga, not talk about, and the people there are so much more knowledgeable about it than me. That's one reason why I joined Acanthite, I actually know things about pokemon and can actually talk about.
Side note: It took me five months on my first forum to make the same amount of posts it took me 2 1/2 to make here.:p
When I first joined a forum was about 4 years ago, so I guess I was ten. It... well, it was Neopets, but it has a forum, so I guess that counts.