I can never actually remember anyone teaching me how to masturbate. Its just something that's always been there as my own private pleasure that I've enjoyed after discovering it myself.
Some of my most intense first memories of it are from when I was younger and on a family holiday. We were staying at this campsite down by the coast. I headed off on the first morning to the shower block while it was quiet. Once there I went in and locked the door and proceeded to undress. As I was doing this I suddenly realised that this was the first time in my life that I was using a public shower and I was nude!!. Oh wow, immediately I got very aroused. Going over to the shower I switched it on and sprayed water all over my penis. It felt so good!.
I was a bit concerned that I would get caught, but just couldn't stop. So I took down the shower head and placed it just over my penis and started to focus on masturbating and nothing else. I just didn't care if someone was in the cubicle next door.
My breathing came shallower and shallower and I started to get louder (thankfully nobody disturbed me while doing this). Eventually I could contain myself no longer and I experienced an incredibly intense orgasm. I ejaculated onto the wall of the shower with a force I'd never experienced before.
That was first real experience of nude masturbation. From such beginnings I learnt a lot and continue to practise today.