I don't know when the first time was.
When I was little, if I put my hands in front of my crotch when I laid on my stomach, it felt good. At night, when I went to bed, I'd lay with my hands between my legs. I figured out that if I pressed over and over again, it felt really good. Then I noticed that if I put my hands underneath my underwear and pressed on it directly, it felt even better. I remember that, after doing it awhile, a feeling would come. It was hard to describe. I remember there was a feeling, and I was trying to keep the feeling and hold it as long as I could, but it came in bursts. Then it would stop. I'm not sure if I would do it more than once a night. I just know it felt good.
I was pressing on my shaft just below the head. I did it almost every night, I believe, and I think it's why I have a downward curve now.
The first time I really ejaculated was in the bath. I think I had stopped doing the dick-pressing thing awhile before that. (There was a point where I shared a room with my sister. One time I was pleasuring myself using my usual method, then she looked over. She was on my left, and my covers had moved JUST enough to the right to reveal that my pants were down, and she could tell the general direction my arms were going. She said she would tell everyone at school if I ever did it again.) I took a bath, and by this point I had seen porn a few times (through an automated ad in StarCraft, for the record). I knew that sex was when a guy stuck his thing inside of a girl and moved in and out. I hadn't figured out that the mechanic that gave pleasure to men during sex was movement up and down his cock, not the fact that it was going in and out of something. I actually tried to stick my cock in between the cushions in a couch once, but it didn't work too well. I remember that I was actually jealous of women, thinking that they could simulate sex for themselves while men couldn't (the mechanic that gave pleasure to women was anything going in and out of them, while men needed something to go in and out of!).
WOW this message is getting longer than I thought it would be. Anyway, I was in a bath, and my cock got hard. I accidentally pressed it funny with my legs, and it felt good. I then, somehow, got this idea. Being half-hard, I would bend my cock in the middle, and stick the tip between my thighs. I would press on my cock over and over again, moving it in and out of my thighs. It felt REALLY good. Then something happened, and there was... stuff, all over my thighs, and my balls. The semen in the water was sticky and really difficult to keep off of me. I remember the white stuff being so difficult to deal with that I didn't leave the bath happy.
I don't know why I did it again some while later, since it was such a huge hassle. As for when I started jacking in the normal way, I don't know.