Here's one of my house rules for ability scores and modifiers.
"The Swords & Wizardry system is much less cohesive than rules systems based on later design, and it follows set patterns less often. Thus, the bonus structure from BECMI has been adapted.
Modifiers are applied as follows:
- Strength: Melee attack rolls and Str-based saving throws.
- Dexterity: Missile weapon attack rolls, thrown weapon attack rolls, AC, Dex-based saving throws, and initiative.
- Constitution: Hit point rolls and Con-based saving throws.
- Intelligence: Int-based saving throws.
- Wisdom: Wis-based saving throws.
- Charisma: NPC reaction rolls and Cha-based saving throws.