I remember getting erections at least as far back as 7 or 8, especially when sneaking a look at my father's Playboy magazines. But I didn't start masturbating until later.
After reading a paperback book called "Boys & Sex" at about age 12 (my father's idea), I got really curious about masturbating. The book had suggestions on several ways to do it.
The problem was, my family was living in a small apartment at the time, while our house was being built...so I would wait until the TV was on nice and loud in the living room, and Mom was making noise in the kitchen, to lock myself in the hallway bathroom. I'd drop my pants and underwear down to my knees and tug away, which felt good, of course, but it didn't bring me to a climax. I'd never had one, at that point. I tried sneaking in Playboy centerfolds, hidden in my pants, but something about the whole atmosphere, with my family talking just a few feet away, just didn't put me in the right mood.
I decided to try another of the book's suggestions. I hid a bath towel in my bed, in the room I shared with my brother. I stayed awake that night until I could hear from his breathing that he was asleep, then pulled my pajama pants and underwear down, lay face down with the towel under my belly, penis and thighs, kind of enjoying the feeling of the cool night air on my bare hips, and the secret nature of what was happening, and I quietly started thrusting.
The rough texture of the towel gave a sweet friction to it all, and as I rocked my hips back and forth, trying to keep the squeaking in the bed to a minimum, I thought about a magazine I'd seen with Vampirella. I imagined waiting until she was sleeping, then slipping those huge breasts out of her skimpy outfit, one at a time, and kissing and sucking on what I was sure would be dark nipples. I didn't really know what any of this would feel like, but I'd seen some x-rated comics with guys doing stuff like this with naked and mostly naked women, and I'd always gotten hard while reading them.
As my thrusts got harder and an instinctive rhythm took over, I fantasized about doing the rest of what I'd seen the cavemen in one of those comics do with (mostly willing) 20th Century girls in cut-off shorts... stripping Vampirella's outfit down until her pussy was bare, getting on top of her, feeling my pubic hair press into hers, and pressing my cock into her.
Suddenly, I started breathing hard, and the thrusts got harder in a rhythm that knew its own way. I felt intense tingling warmth spread from my hips across my back and legs, my ears were ringing, and I could feel something warm spurting from my cock.
I remember after the orgasm faded, being a little in shock, and feeling the slick wetness, thinking, "I could be a father now."
I rested a little, listening for any signs I'd awakened anyone else (all clear), then used the rest of the towel to clean up, hid it under my bed for the moment, and got back into my underwear.
Though thrusting into a bed and towel turned out to be my favorite way (stronger orgasms), I tried a few other things from the book. Putting a finger in my rectum while jerking off, for example, but I soon learned I preferred Vaseline-coated toothbrush handles and candles.