My first masturbation was an accident. I was 12 years old, in seventh grade. I'd just taken a bath and was sitting in our darkened family room watching TV with my family. The room had an "L" configuration, so that the doorway (and about four feet into the room) wasn't visible to anyone sitting in the main part of the room. That's where I was sitting, on the floor, out of view of my family, naked and warm from my bath, covered by a lightweight thermal blanket.
While everyone else was watching TV, I was enjoying the feeling of being naked, my stiff penis touching my (still hairless) inner thigh. To enhance the feeling, I began rubbing the head of my penis against my thigh. It felt so good! So I kept rubbing it, back and forth, back and forth. The feeling became more and more wonderful. My arm action became less coordinated and almost spastic. And then...I came! I hadn't known what an orgasm was. I'm not sure I even knew the word yet. But I knew it was amazing and I knew I would do it again the next night. And so I did.
It wasn't until I was 15 years old that I masturbated any other way than by rubbing my erection against my thigh. By then I'd begun to spurt a little bit. And I was inspired to use my hand as a substitute vagina - I so badly wanted to know what that would feel like! And so I discovered the "conventional" way of masturbating, which is how I still (usually) do it. Every once in a while I go back to the penis-rubbing way, out of nostalgia (and desire for a less-familiar sensation).
That same year, 15, I decided to keep statistics on my masturbation, for a full calendar year. (I'd seen a college textbook of my mom's, with statistics from Masters and Johnson, about masturbation frequency.) I still have the data sheet I compiled that year (40 years ago!). That year I masturbated 242 times, or four-to-five times a week. The most times I ever orgasmed in a day was three - a number of occasions. The most consecutive days I masturbated was nine. The most consecutive days I went without masturbating was six (I wanted to see how long I could endure). And I kept track of all the different places I did it - in the tub, out of doors, at another person's house, in a car. I can locate the sheet and report on all of this if anyone cares! But now I think I need to go masturbate! :-)