Only call for a roll when there is dramatic uncertainty. If the outcome is obvious, skip the dice.
Difficulty is absolute, not relative to level. Compare it to the relevant Attribute only unless the fiction demands otherwise.
Fast. Usually one shift. A second shift is rare. Other players may pile on with suggestions, but do not turn this into a negotiation phase.
Terrain, visibility, injuries, Rattled, Assist/Bolster, cover, time pressure, magic, tools. Rattled is −N to all tests.
SLT is always spent before the roll, as pre-roll Luck. Combined pre + post Luck on one roll cannot exceed 3. Pre-roll Luck also lets the player reroll 1s and 2s (never if the raw result is 11).
Post-roll Luck still legal: 3
Lowest die is tens, highest die is ones, middle is ignored. If all three match, it is a double and situation/Luck shifts do not move it. Pre-roll Luck / SLT lets you reroll a 1 or 2, one die at a time.
Rerolls cannot make the roll worse. If they would, keep the original dice.
Post-roll Luck also reduces GM Action severity one step per point. Total Luck on the roll still cannot exceed 3.