MadLordOfMilk
First Post
Having used advice found in basically every post in this thread, it's definitely helping a lot with getting the system down. Thanks, all! 

I've often thought that it would be helpfull if there was some sort of "tutorial dungeon" to introduce new players and DMs to the game. If there's something out there like this, I haven't seen it.
Each room of the dungeon would focus on one game concept, and be written to help new players and DMs easily practice and understand that one concept.
So using pregenerated characters, the players would enter the dungeon, and the first room would involve some sort of puzzle or situation that would teach them how to count off squares of movement. Once they understood how to move, the next room might require them to shoot at a target with a ranged weapon, and then another room where they would have to swing to hit something with a melee weapon. Then a hallway with traps in it, where everyone could learn to find and disable traps and/or make saving throws.
Then into a cave with no floor, but with various narrow ledges and rough wall surfaces. The only way across is to play through and understand how to do Acrobatic and Climb checks. If you fall, you find that the bottom of the cave is flooded, and you get to practice making swim checks. Eventually the players would find their way down to deeper levels, where more difficult rooms would teach things like Attacks of Opportuity, or spell casting, or cover and concealment. The final room would put it all together using everything that's been learned in a final battle with a challenging monster.
By the time the DM and players have completed the entire adventure they'd have a good idea how all the basics work. The tutorial dungeon has "walked you through" how to run/play an adventure.
And it could be helpful even for more experienced players. Still having trouble with climb checks? Go back to the climbing cave and practise some more. Still don't quite understand what triggers Attacks of Opportunity? Go back through the Attacks of Opportunity room. Or the flanking room. Or the "hallway of how to break down doors." Or the "temple of how healing works."
It wouldn't be a "realistic" dungeon at all, but it would sure help with the steep learning curve for people just getting into the game.
This was a great idea brought to me by a friend that's just getting into the game and needed help grasping the basics. I'm currently working on one myself and will post the results on here later with the "finished" result.
Would love to help. I can make maps, or fill in some encounters. This would be a splendid 3pp product...
PM me if you'd like some input or help.