Well, when I was about seven or eight a friend of mine owned a horse (a very rare thing in Las Vegas, Nevada) and her brother lifted me up on his back one day. I will never forget the feeling of the warm sides against my legs, and fingers holding onto mane, and hearing the horse munch the grain her brother had given him before he'd sat me up there. I don't even know what their names were anymore, but boy, do I remember that.
Then my aunt led me and my two younger sisters around on a horse when I was ten. I loved it, despite the fact that I was fighting to keep from falling off, since both my sisters were clinging on behind me.
First time with actual tack and no one leading me was when I was 13. It was really sporadic for a couple years, until eventually I made friends with a really wonderful lady who taught me a ton and let me ride regularly. More than that, she taught me to ride Western, English, saddleseat, and even a bit of bareback. Then, when I got a job, I took riding lessons every week.
Then I went to college, and now I'm lucky to ride twice a year. But I graduate in a few weeks, and as soon as I get the extra money, I intend to get back into the saddle.