In particular, a science fiction fan. I'd been a reader of science fiction and fantasy in my childhood, starting with the Scholastic Book Club paperbacks that I regularly bought in elementary school, including books by Robert Silverberg, Lester Del Rey, and Alexander Key.
Later on I discovered the Heinlein juveniles and the classics by Jules Verne and H.G. Wells. Then when I turned twelve or so I started reading Jack Vance's Dying Earth stories and then was passed Tolkein's Lord of the Rings trilogy by my sister and I was hooked. I also read Frank Herbert's Dune, Heinlein's Stranger in a Strange Land, plus some Bradbury, and Harlan Ellison's stories and anthologies. I also read and had every Tarzan novel, so by the time I left home and went off to college I'd pretty much graduated from the public library's SF&F section, with some skipped courses left unread on the shelves. Not that they were required.
In the meantime I'd also seen some SF TV, but it had been drivel like Lost In Space, Time Tunnel, Voyage to the Bottom of the Sea, etc. I somehow missed the original run of Star Trek but when I was a young teenager some of my buddies and I started watching afternoon reruns in the early 1970s after we were out of school, and we saw them all and enjoyed the experience. Media SF was to me fun, but not as deep as what I'd been reading. One thing I did miss out on was the SF&F peridoicals of the day, so I never saw those ads in the back talking about conventions and fandom.
Then after I'd gone to the University of Iowa for a semester in 1977 (after being a semi-truck driver while I was trying to figure out what to do with my life - long story), Iowa Public TV in the spring of 1978 started running episodes of Dr. Who at 10pm, Monday-Thursdays and somehow I discovered it and since I had the best color TV on the dorm floor I was living on, there was a gang of several guys who gathered every night to watch a half-hour fun-filled episode. One of the people there, Mike Miller (aka "Spacey"), was a member of a group called SFLIS (Science Fiction League of Iowa Students) and told me about them and that they met weekly at a downtown bar, The Mill, and if I'd be interested in attending one. I was, and I did, and I had fun talking science fiction with them over the next few semesters and watching Dr. Who until it was taken off the air in March of 1979.
Then in the fall of 1979 I was involved enough with the club to help a little with putting on a convention, which was ICon 4, that November. I wasn't responsible for much and as a result had a great time while all was not so well otherwise. (It's known as DisasterCon in ICon lore for a good reason.) But I still liked what I saw of what was called "fandom" and the next spring went to another convention, Minicon, in Minneapolis, and then went to the next ICon in Cedar Rapids in the fall of 1980 and to many other cons since. It's been great fun, mostly.
So thanks Spacey for introducing me to fandom, and I'll see you at ICon 38 in November!