My LotFP saving throw houserules:
Reflex saves require you to take physical action against a physical threat or attack of some kind (breath weapon, falling from a great height).
Resistance saves require you to withstand toxins and disesase (such as poisons or plagues)
Refusal saves allow you to withstand illusions and magic and trickery.
Each saving throw is against a difficulty. Difficulty ranges from 12 to 20, and you roll over it just like a "to-hit" roll against ascending armor class. A breath weapon attack would have a difficulty of 12 is some minor-league 2 hit dice creature, and a difficulty of 20 is for an ancient black dragon.
You roll your d20 and try to equal or beat the difficulty. In each case, you add any bonuses for high attributes.
- For a Reflex save, you add any Dexterity and/or Intelligence bonuses to your roll.
- For a Resistances save, add Strength and/or Constitution.
- For Refusal, add Wisdom and/or Charisma.
For example, a character with a Strength of 13 and a Dexterity of 16 must dodge falling boulders. The Referee says that the difficulty is 15. The player rolls a d20 and hopes for a 15 or higher. The roll is a 13. However, because of the high Strength and Dexterity scores, we add 3 to the roll, making it a 16. Saved! The character dodges out of the way.