A brief overview of the rules

[Gerrtt]

If you had new players and were going to do a one-shot type deal to introduce them to the idea of the game, what are the key ideas/concepts/rules that you would would want them to know just to keep the game running remotely smoothly. Let's assume you want to put together a one page document.

I'm thinking:

Melee/Ranged attack basics
Basic Spell mechanics
Movement
Skill/Ability checks
Attack of Opportunity

What else?

[Telonius]

Social Encounters (i.e. make sure they know that "attack it!" is not always the only option)
Saving throws
Changes to ability scores (through spells, poison, ability damage, etc) and how that affects combat
Traps/Secret Doors (this is covered in "skill checks" but it's important enough to carve out a specific example or two).

[Shining Wrath]

Start with the basic D20 mechanic.
Attack: roll D20, add these numbers, compare to this number.
Save: roll D20, add these numbers, compare to this number.
Use skill: roll D20, ...
Then give them examples of each of the skills and when they might be used. Open Lock is pretty obvious; Diplomacy, not so much.