Do you want to introduce new players to D&D? You don't want to overwhelm them but give them a good time. They should get a taste of the awesomeness of pen & paper games. But you don't want them to get confused by the mechanisms.
Plus, you might be a fresh Game Master yourself.
Whether you are an experienced Referee or a fledgling Game Master, you should check out this video by Drunkens & Dragons.
But, you say, this goes on for about an hour! I don't have the time!
I got you covered.
a) watch the summary starting at 00:47. So, that's only about 15 minutes.
b) read along for the main points.
Basically, Hankerin gives you a minimalist ruleset that's loosely based on D&D. Low entry point to get your players hooked. Explain the rules while playing.
Bonuses, not stats.
Ask your players what kind of character they want to play. They should come up with a name, a description. You give them some bonuses. Give him some hit points, 10 or 12.
For example, George wants to play a guy like the Gray Mouser. You, the Game Master (GM) give him a +1 on Dexterity. George should describe his guy and give him a name.
We don't use the attributes. We just roll a d20. We might apply a bonus but that's it. No skill system, no six stats. Done.
Magic = prestige
No spellcasters at low levels, magic is mysterious. The wizard is just a dude with a book and a lot of studied knowledge. The GM might allow them to cast a spell. Roll to see if the character remembers the spell correctly. But then it just works, no complicated rules. This should wet the players' appetite for the spellcasting classes later on.
For now, all characters are fighters or rogues. Let them become magical during your campaign.
Ease your players into the magic rules.
How Does the Game Work
What's a turn?
The player describes what he wants to do. The GM lets them roll against a target number. Then decide the outcome.
For example, a player wants to intimidate a foe. He has to tell the GM how he wants to accomplish this (with a display of strength?). Then he rolls. Let's say it is barely a success (like a 12 vs. a target of 11). The GM might now explain how one opponent backs off warily but the others are not impressed.
What's the target number?
One Room DC
The whole room has one difficulty. Mid-level it (10 - 12) and the dice rolls will make it go crazy.
Simple Turn Order
Who goes first? Everyone rolls a die. Highest roll wins and then we go clockwise.
Simple Monster Stats
|1||6 - 12||1d6|
|2||12 - 18||1d8|
|3||18 - 36||2d6|
|4||36 - 48||2d8|
Make the descriptions cool, not the stats. You don't even have to read the monster manual, make it up.
Spaces, not Feet
Tell your players how many spaces they can move on the game board/map. Don't tell them 30 ft., say: "You can move 6 spaces on your turn."
3 Principles of Room Design
The timer is some kind of doom that's approaching. E.g. a goblin army that will march in. The room will get flooded etc. Roll a polyhedral (e.g. a d4). The result shows how many rounds it takes until the threat happens. The die acts like a counter. (So, if your result was a 3, make sure to flip the die to a 2 at the start of the next round.)
The treat is stuff the players can find and use. Treasure, loot, tools that can turn a situation into their favor. Give them healing potions, they don't have magical healing.
Threat is the immediate danger they are in. Monsters, traps, etc.
This is an easy way to get new players into the role-playing game hobby. Strictly speaking, it is not D&D, the system. But it is a stripped-down d20 game that can scale up to D&D.
You can also use the principles to make your "advanced" game better.
What Others Say
What's way more interesting than the inner minimalist mechanics is the way he builds the game and how he delivers its intentions:
- the Describe/Roll/React sequence is teaching the rhythm of a RPG
- the simple turn order to resolve this task faster with less bookkeeping
- the simple monster stats to avoid having too much detail on every monster and sketch NPCs/Monsters in a fraction of a second,
- the Timer/Treat/Threat also gives fundamental assets for the GM to build each room with an interesting challenge to overcome,
- the one room DC - it has interesting effects if you graduate your rooms, the more you get into the dungeon, the bigger the DC (so, mechanically, the bigger the threat, the better the Treat),
- Spaces not feet: again, less bookkeeping ; it reminds me of the "Distances" section in The Black Hack.
With that kind of framework, the ruleset won't get in your way when you want to build your story and the characters are free to act ; but most importantly, players are learning how to RPG and your GM is also learning how to throw interesting challenges at the PCs.