Being a kid that grew up with access to the internet, I clearly had the opportunity to look for pornography when I wanted it. Granted, this wasn't a purposeful goal as much as an accidental happenstance, or serendipitous moment. Here is how it all started, or at least what I can remember.
It happened on a school computer in junior high, in the schools library. I had to do some research and clicked from Google to Google images to discover a photo. This was not an erotic photo, or at least, not to most people, but it centered around bondage, slavery, or some sort of tying up as that is how I realized that you could Google search for porn. The thing is, back then the stuff that was blocked was all mainstream porn that consisted of people having sex, not covering the fetish interests of a teenage boy.
It was a combination of this, exposure to the American version of one episode of "Don't Forget Your Toothbrush" (featuring some fetish sex items like a ball gag head harness, a tongue vibrator, and some other dirty items), and reading up in the Webster's dictionary some words associated with bondage like "fetters" and "manacles".
That is the jack off material that got me through my teenage years until I figured out how to look for better porn, became of legal age to enter an adult store and buy a dirty DVD, and had a credit card to buy sex gear online as the shop in town didn't have anything. ( The DVD below was my first, it was cheap, in more ways that one and didn't really do anything for me, but I think I liked the school uniform thing at the time)