I suspect most people will say that the best way to learn a new game is by playing it, and I can’t disagree with that advice, but I’d add that playing it with someone who knows the game well is really the best way to learn a new game.
Of course, that’s not how I learned how to play role-playing games. I came into the hobby cold, with little to no understanding of what a role-playing game was.
I was just ten years old, and my brother had convinced me to buy the Basic Dungeons and Dragons boxed set on the basis that there was a board (on which I thought I would be able to use those cool miniatures I had seen in the store). Of course, there was no board and it would be many years before I started buying and using the miniatures, and many, many more before I really used them heavily.
Nevertheless, as compensation for having deceived me, he “let” me be the Dungeon Master. That didn’t last too long, as I was only 10 and knew nothing of RPGs. But I made my best effort and tried running the introductory adventure.
Later, my brother took over for a short time as DM, and then an older cousin for the next year or two. But, we were all learning together and we didn’t necessarily learn any “best practices”, not by a long shot.
I began running games with my friends soon after, and we went through all the worst abuses of gaming. Monty Haul treasures beyond belief, battles with unspeakably powerful foes that we easily bested, and then the other extreme, killer encounters that kept wiping out the party.
My education on learning RPGs and various new games through most of my life was on my own from the books. It worked for the most part, and I think it’s probably one of the most common ways of learning RPGs, but it could have been better, and I would have saved myself from committing many of the errors of youth. But, then that’s what youth is for, right?