Brendan of Untimately has organized a fantastic set of simple rules questions that should make it easy to translate between referees. Here's the answers for Partholon:
Ability scores generation method? 3d6 in order, make a one-time swap of any two scores.
How are death and dying handled? At 0 hp, you are incapacitated and might die. If you survive, you will be saddled with a hampering injury. Details here.
What about raising the dead? Bring offerings to a sacred grove of dryads and score a good reaction roll.
How are replacement PCs handled? So far: promoting a retainer to PC status. PCs can also designate heirs to their wealth (minus 10%). New characters always start at 1st level.
Initiative: individual, group, or something else? Group d6 at start of encounter, high roll wins, ties lead to roll-off. Groups alternate for remainder of combat.
Are there critical hits and fumbles? How do they work? Natural 1 always fails and natural 20 always succeeds. If you're trying some fancy stunt, the referee may interpret rolls more elaborately.
Do I get any benefits for wearing a helmet? It could save your life at 0 hp. It's definitely helpful when green slime or spiders are dropping on you from above.
Can I hurt my friends if I fire into melee or do something similarly silly? Yes, absolutely. Ranged attacks target the melee group, with hits distributed randomly among the combatants.
Will we need to run from some encounters, or will we be able to kill everything? I'm often surprised by what the party manages to kill, as well as what they have to run from. Setting things on fire is usually a good idea one way or another.
Level-draining monsters: yes or no? Yes, but you can recover the lost levels with extensive bed rest.
Are there going to be cases where a failed save results in PC death? Usually a failed save just means you take massive damage, so it's likely to be fatal, but there remains a slim chance of survival.
How strictly are encumbrance & resources tracked? Pretty strictly, but I use a simplified encumbrance system similar to LotFP.
What's required when my PC gains a level? Training? Do I get new spells automatically? Can it happen in the middle of an adventure, or do I have to wait for down time? With rare exceptions, XP and advancement is handled only during down time, and no training is necessary. Clerics get new spell access automatically. A magic-user will be offered a new spell by his/her mentor at each level-up through 4th level.
What do I get experience for? Treasure, defeating foes, unlocking new campaign resources.Magic-users get xp for money spent on each original project (e.g. the first time you make a given type of potion).
How are traps located? Description, dice rolling, or some combination? If the party is moving at mapping/sneaking speed, I assume they're looking for signs of traps. The locations of traps are therefore usually fairly obvious. How to get past them is a puzzle for the players to work out. Once a strategy is in place, dice rolls help to see if anyone goofs up. Influenced by Ben Robbins "Bad Trap Syndrome," part 1 and part 2.
Are retainers encouraged and how does morale work? Retainers are awesome, and I use B/X morale.
How do I identify magic items? A magic-user with proper equipment can run some tests and eat up time and resources, and it might even work. Or you can just try doing things and see what happens.
Can I buy magic items? Oh, come on: how about just potions? Not currently. Opportunities may be discovered in the future, though.
Can I create magic items? When and how? The rules I use are modified from LotFP. I'm also looking at the Crimson Pandect for additional refinements.
What about splitting the party? I discourage it under most circumstances. As a tactic for outflanking opponents or investigating an enigma, it's fine. As a strategy for exploration, I'd rather not deal with it.
And I'm appending a couple of extras:
What kind of saving throws do you use? Modified from Swords & Wizardry: Whitebox, one target number based on class and level, with modifiers based on class and ability scores.
What's your base currency? Prices and XP are based on a silver standard.
Update: Beedo, of Dreams in the Lich House, had some good add-ons.
How is alignment used? Among PCs, it's an ethical measure of just how trustworthy the character is, in a Sword & Sorcery or Spaghetti Western way. Among Monsters, it frequently reflects a more cosmological significance.
Are demi-human level limits enforced? Until the players find and make alliance with some demi-humans, there aren't any in the party.