Optional Rule: Automatic Success
Sometimes the randomness of a d20 roll leads to ludicrous results. Let's say a door requires a DC 15 Strength check to batter down. A fighter with Strength 20 might helplessly flail against the door due to bad die rolls. Meanwhile, the rogue with a 10 Strength rolls a natural 20 on her first check and knocks the door from its hinges.
If such results bother you, allow automatic success on checks for characters with high ability scores. Under this optional rule, a character automatically succeeds on any ability check with a DC less than or equal to the relevant ability score minus 5. So in the above example, the fighter would automatically kick in the door. This rule doesn't apply to contests, saving throws, or attack rolls.
The downside of this approach is its predictability. Once a character's ability score reaches 20, checks of DC 15 and lower using that ability become automatic successes. Smart players will then always try to match the character with the highest ability score against any given check. If you want some risk of failure, you need to set higher DCs. Doing this, though, can merely aggravate the problem you're trying to solve: higher DCs require higher die rolls, and thus rely even more on luck.
You can modify this rule to account for proficiencies using an additional option. If a character can apply a proficiency bonus to the check, he or she automatically succeeds if its DC is less than or equal to the relevant ability score. If you don't mind predictability, and you can resist the temptation to increase DCs, you might find that this variant speeds up play and focuses attention on truly difficult, tense situations.
Source: DMG, page 239
If such results bother you, allow automatic success on checks for characters with high ability scores. Under this optional rule, a character automatically succeeds on any ability check with a DC less than or equal to the relevant ability score minus 5. So in the above example, the fighter would automatically kick in the door. This rule doesn't apply to contests, saving throws, or attack rolls.
The downside of this approach is its predictability. Once a character's ability score reaches 20, checks of DC 15 and lower using that ability become automatic successes. Smart players will then always try to match the character with the highest ability score against any given check. If you want some risk of failure, you need to set higher DCs. Doing this, though, can merely aggravate the problem you're trying to solve: higher DCs require higher die rolls, and thus rely even more on luck.
You can modify this rule to account for proficiencies using an additional option. If a character can apply a proficiency bonus to the check, he or she automatically succeeds if its DC is less than or equal to the relevant ability score. If you don't mind predictability, and you can resist the temptation to increase DCs, you might find that this variant speeds up play and focuses attention on truly difficult, tense situations.
Source: DMG, page 239