[d20house]

Unless stated otherwise, assume rules are as given in d20. I recommend this 3.5 SRD, as it countains all the necessary foundation material. D&D 3.5 will also work.

While I pilfered a lot of good ideas from Pathfinder, I'm still using d20 as my default.

DM Fiat

The first rule of roleplaying is that the DM can do no wrong. I'll be trying to highlight DM-fiat in order to speed the game, rather than bogging down in rules minutia. A few DM tips to help this along:

Tough or Challenging?: Most DCs are in the range of 15 (Tough) to 20 (Challenging). So, most of the time, picking one of these two DCs will have you decently covered. (See Skills Checks for more.)

"Roll first, ask questions later": Frequently the difference between DC15 or DC20 won't actually make a difference because of the roll. So roll first, and then decide what the DC should really be only if you have to. This is easier if you don't tend to name DCs to your players. Instead, ask what they rolled and then give the appropriate response.

30-second lookup rule: If you can't remember a DC or effect, ask if anyone else can. If you have rule-lawyers in the group, see if they can do a lookup and recitation within 30 seconds. If not, just call it and make a note to yourself (including what you thought the rule probably was) and look up the details later.

Core Mechanic

... is still roll d20, add modifiers, and compare to a DC. A roll >= the DC is a success; less is a failure. But the results can be characterized beyond this simple binary distinction. Each 5 points above or below the DC translates to a different Degree of Success (DoS):

Automatic Success and Failure

A natural 20 roll means the attempt is at least barely successful, regardless of modifiers. If the roll would have already been a success, it succeeds by one higher DoS than normal or receives some other appropriate benefit (such as a critical threat).

A natural 1 roll means the attempt is at least a poor/mild failure, regardless of modifiers. If the roll would have already been a failure, it fails by one worse DoS than normal or suffers some other appropriate mishap (such as a dropped or broken tool).

Checking: Skipping Rolls

Take 20: If time or failure is not a problem, the player can keep trying until they get it (if a roll of 20 would be enough).

Take 10: If not rushed and distracted (usually not in combat), but still need to get it right the first time, a player can Take 10.

Take 5: (only occasionally useful) Even if rushed, a player can Take 5. This is handy for known DCs where the player just wants to succeed--such as Heal checks to stablize a companion, etc.

Take 1: If the player's total modifier to the roll is greater than or equal to the DC, the task is so trivially simple that failure should be impossible, even if rushed. (Taking 10 in this case would produce a Great result.) No roll should be required, thus avoiding the possibility of automatic failure. (Assume a die result of 10 if determining outcome is necessary.)

Default passive rolls: The DM can assume characters Take 10 (if they're paying attention) or Take 5 (if they're not) on their Spot and other passive checks. Thus, even the fact of making a roll is not revealed.

Group rolls: The DM can roll once for the whole group, and then apply each person's modifier to that roll see who succeeded and who failed. (This works nicely for speeding initiative checks, group Spot checks, etc.)