In the beginning

The first time I DM'd a game of 1st edition D&D, I didn't own a rule book, I hadn't prepared an adventure, and I'd never met all but one of the players I started with.  There were no minis, it was all 'theater of the mind', and I'd only played the game as a player 3, maybe four times.  Sounds like a recipe for disaster, right?  I don't remember much of what happened.  I let each player start with two characters with the understanding that there would be a high mortality rate.  Two characters did die that night, one turned to stone by a basilisk and one eaten by a black pudding that dropped from the ceiling over a pile of bones and a few coins (no one looked up).  I had no concept of what challenges were appropriate to a 1st level party.  There was a little griping, but mostly the players liked the session, and we kept playing for nearly 5 years afterward.  Some of the players said I was the best DM they ever had.

From that brief experience, I'd already become frustrated with some of the mechanics of the game (the monster's taken 50 points of damage, but still functions the with the same effectiveness as when he had taken no damage?).  But I didn't care about mechanics, except as they affected the players feeling like they were having a cinematic experience.  I wouldn't have put it in those terms then.  What I wanted was to evoke the kind of reaction I had had like the first time I saw the movie 'Highlander'.  I wanted their imaginations firing on all cylinders.  I wanted them to feel at least on some level that they really were in another world, being another person, experiencing things that couldn't happen in the real world. 

I've continued to play this way up through 4e.  I ignore or modify rules when they don't fit the experience I want to create in the mind of a player.  Wealth by level is a good way to keep a gauge on the relative power level of your players.  A better one?  Through monsters at them with varying power levels and see how they do.  I've never been a system master.  Oh, I read the rules through, many times, and I reference them often - there has to be a common framework that the players have the same access to as I do or the game is just arbitrary with no way for the players to meaningfully interact with the fantasy setting I create.  But if there is no magic carpet available at an appropriate level for my party in 4e rules and I want a flying carpet shop in the town my players are entering, I make something up, rules be damned.  Does this render some challenges like trying scale a cliff irrelevant?  Perhaps, temporarily.  But how hard is it to bypass?  Can I still invent challenges that are appriopriate to their capabilities despite this?  Of course.

The system doesn't matter to me.  The game and the story has always been inside my head.  I play the game/edition that my current group plays.