Odd. My first GM was another kid about the same age. His step-father ran games for him. He had a lot of Gygax "players dont read the DMG/MM" vibe going on. He had this concept that you leveled as a player yourself, to the point you could actually GM. Though, you could only GM up to the point of level you had yourself. I have no idea how any of that worked and we only did two sessions.
My (technically) first D&D experience was trying to run the Moldvay box basic "Haunted Keep" for my mother and sister in 1982.
It went meh. They didn't get it.
Then, a year later, I tried to play AD&D with a high school club.
It went terribly. They let me watch for two hours, and then they suggested I not come back again because there would "never" be room for me.
It was the summer of 1978, and I was almost five (my best friend has just turned five). My older sister (9), his older sister (9) and brother (7), and two of my older cousins (11 and 12) invited me and my friend to play D&D with them. My cousin (11) ran the game.
At almost 5, I didn't really understand much of the rules. Mostly, my sister and the others would ask me what I wanted my magic-user ("Dartson") to do and tell me which dice to roll. I named him Dartson because he would throw darts after his spell was gone.
I was hooked from the beginning. I asked my parents to buy me books for my birthday a couple months later when I actually turned 5. I read them and re-read them. We learned how to play and made up the stuff we didn't understand.
First time playing was in sophomore year of college. We played 3.5 And it's how I met my wife. I played a dwarf paladin with absolutely horrible stats. Our party was charged with protecting an artifact that could banish Asmodeus. We promptly lost it when we tried to hide from an orc patrol, nobody rolled above a 3, and we got our butts handed to us. All in all, fun times. Made some friends and I loved the game.
First time running a game was a semester later. Yea, I'm pretty sure it was a hot mess. I think we knew maybe half the rules in the book. My story was all over the place, dungeons were ripped from whatever video game I had on hand, (Zork!) and XP and Wealth By Level were given a fleeting kiss goodbye early on. But, we had fun. And kept playing through most of college together.
I was just a student at a large midwestern university, and I never thought something like this could happen to me. But one week, I was late getting to class, and I had to sit in the back next to the gorgeous graduate teaching assistant. Little did I know when she asked if I was interested in dungeons what would await me!
It was back in 4th grade (1980), and I don't really remember it. All I remember until I got my hands on Moldvay was that we entirely winged it, without dice. You literally had to describe what you were doing as the player, and then as DM I described the result. No dice rolling, we had a blast playing for a couple years that way.
I do remember the first time we used the full ruleset and dice - the Haunted Tower from the Basic book, in '86. The party died in the pit trap in the entrance, so we started over and it went a bit better from there.
I was part of a massive party that stormed my cousin's dungeon in 1975. The party had numerous PCs, lots of henchmen, and even some pets. PCs were of various levels. I don't recall what class I was, but I do know I was 1st level. I also was used as cannon fodder with a combat with a vampire and her minions and died horribly.