What a question, I'd have to say someone else taught me everything I've learned about fishing, either in person or in print. I don't think that there will ever be a magazine as focused on teaching as the late 80's thru early 90's In-fisherman was. The mid thru late 70's Fishing Facts magazines shaped much of my attitude and approach to fishing in general.
As far a people showing me stuff, back in the early 80's I thought that a jig and eel was the best bass bait there ever was. I hadn't ever caught a fish on a spinnerbait, and had only limited success with a Mepps style spinner. A professor pal of mine gave me a lesson one afternoon on spinner bait fishing to the tune of 40 or so to 2. A very simple idea - spinner baits skimming the tops of weeds in 4 to 6 feet of water.
I didn't have a clue about pitching until I fished a few BFL tournaments. I was whining about how I was getting back boated all the time and I got told to learn how to pitch, it would open up many more casting angles to me. True fact. Took me nearly a whole season to get any good at it and now10 or so years later, I'm still not a master at it, but I don't suck either.
Last summer, fishing with a buddy, I was whining about how I couldn't catch a fish in slop on a frog. And I had spend some money on decent gear. My bud proceeded to take MY rod & reel, with my black frog tied on and proceeded to catch one fish in the 4 lb range and a couple more slot fish in the next 5 minutes.
I'm still not any good at frog fishing, but I've seen it done now and I have hope for future seasons.
So there are a few anecdotes on the subject of how I've learned what I've learned