This rule was formerly too narrowly defined as a combat-only rule. It was:

Percent Strength Rule: A Character using a hand weapon can choose a “Full Strength Blow” which gives a +1 Damage, but -1 AL. A “Careful Blow” gives -1 Damage, but a +1 AL. If you use the Fatigue Rule then a “Careful Blow” also reduces the Fatigue used per Melee to ½ point. A “Precision Blow” has a -2 Damage, but a +2 AL, and gives a +2 on the Critical Hit Multiplier roll if a Critical Hit is scored (maximum critical hit multiplier = 😎 indicating that the “Precision Blow” hit the exact spot intended.

It has been simplified and extended to cover all skills as follows:

Strength Effort Rule: A Character can choose to employ a “Full Strength Effort” which gives a +1 Effect (such as Damage, or any other effect), but -1 on the Skill Level. Conversely, a “Careful Effort” causes -1 Effect, but a +1 Skill Level. A “Precision Effort” causes a -2 Skill Level, but gives a +2 on the Effect. So for every modifier on one side, apply the opposite modifier on the other side. Effects can either be point based, or narrative, depending on what the Player states the Character is attempting to do. The GM may adjudicate Narrative results.

I think this is an improvement, and thanks to Donovan for inspiring this updated rule.