At a job I worked at, when I was 14, I found a pack of cigs someone had left behind, and I opened it up to see if there were any left. My buddy and I would sneak cigs at this junk yard next to work, so we were always lookin' for smokes. Well, this pack just happened to have a joint in it. I stayed the night at my buddy's house, and we toked up at about 1 in the morning outside his window. Nothing happened but I pretended it did. That was the first and last time for a while.
About two weeks before my 17th birthday, I was hanging out with friends, and I had been a straight edge for about 2 years, when a buddy of mine offered to toke me up. I wasn't sure, so I did some research for a week, and decided that I wanted to try it. It was lonely being the only straight edge kid, and I wanted to reconnect with some friends who had been smoking pot for a couple of months. I smoked a joint with two of my buddies, and I only slightly felt it. I thought, damn, this isn't near as crazy as I've heard. Then, about 2 days later, I went over to one of my buddy's good smoking friend's house. He had a six foot bong, and a three foot long shotgun tube, and several little water pipes. I took one huge rip off the shotgun, and I then took a huuuuuge rip from the six footer. I ran out of the apartment and puked my guts out over the railing of his deck. I came back in, rinsed my mouth out, and proceeded to be the highest I have ever been. I know I asked at least twice if this bud had anything else in it. I mean I had tracers that were well over 3 feet long. I remember listening to Jimi Hendrix's Star Spangled Banner, and I felt like I was on a rollercoaster controlled by his guitar. Since then I have only quit once, and that was for a years probation on this thing called drug court because a group of us got caught with weed. I have taken a few t-breaks, but that's about it.
Weed is something that I think should be experienced in your upper teens, but I also realize that the world is not perfect and some of my friends have smoked it since they were 10, and are successful people anyways. I know I wouldn't toke out a person younger than 18 nowadays, but that's just because I rarely hang out with anyone younger than 22. I also agree with wthanna, about the prohibition thing, and people saying "think about the children". I may have tried green at a young age, but I didn't get drunk until I was almost 18. That was also when I decided that our government was fucked up, and had the wrong substance vilified. I never woke up with my shirt missing, and feeling like shit on weed.