I make no claims to have had a very exciting introduction to masturbation, but since I have enjoyed some other stories, here is mine.
I started puberty at 11 - it seemed that one day I was hairless and the next day I had sprouted a crop of half a dozen wiry hairs around my still little cock. By the time I was 12 and a half, I had a neat little bush. I should also mention that I am happily intact. For as long as I can remember, I had always pulled my foreskin back and to wash underneath when bathing. From maybe about the age of 10, I had preferred to shower, but my penis hygiene activities in the shower carried on as in the bath.
By the age of 12 1/2 my growth spurt had started and I had also found that now I always got an erection when washing my penis, but it had always subsided by the time I had finished showering. However, my penis had also been growing fast, and I had noticed lately that I had to gently pull my foreskin back over the head of my erect penis - before it had just rolled back itself. One day though after washing my penis, I pulled my foreskin back and with the shower water squirting onto my crotch, I realised that it felt quite good, so I repeated the action. It felt so good that I carried on pulling my foreskin back and forward over the glans. My penis was now harder than I could ever remember it, and my glans was like a shiny purple plum that kept getting swallowed. After a short while, I felt that I was going to piss - this didn't worry me as I had often had a piss in the shower. But this time no piss came out. All of a sudden my knees gave way and I sort of slumped against one wall of the shower cubicle, and this stuff squirted out.
I could see straight away that it wasn't piss - the first 2 or 3 spurts hit the opposite wall of the shower cubicle and slowly dribbled down, while the rest went onto the floor and was quickly washed away. It looked like thick brown custard, unlike the creamy white that I later found out was the usual colour of spunk.
I had never been told much about sex, and I was worried that I had in some way harmed myself, but was too shy to speak to my parents about what had happened. The next day at school, I told my best friend about it and he gave me a funny look and asked if I really had never heard of wanking or spunk? Well, I had heard the words before, but never really knew what they meant. But reassured that it was a normal experience, I tried again in the shower the next night, and ever since I have usually wanked at least once a day, even after I started in my later teens with girls.