(Here is a house rule swiped from HackMaster.)
In addition to the whole number score, each ability also has a fractional component. As you gain experience, your fractional scores will slowly increase, and you will improve in your capabilities.
To determine your base fractional scores, roll a d% for each Attribute. For most gameplay purposes, you can ignore the fraction associated with the ability. For example, a character with Strength 5.74 would still be considered to have Strength 5.
At each new level gained, you increase your fractional ability scores by a given die roll according to your class (as noted in the table below). You only gain fractional increases for experience gained through actual play. If you start a new PC above 1st level, you do not get to roll for fractional advancement until you actually earn a new level.
When a fractional ability score exceeds 100, the whole number score is raised by 1 and the 100 is discarded.
Fractional Ability Score Advancement
Ftr M-U Clr Thf Hun Psi Strength d20 d4 d10 d8 d12 d6 Intelligence d4 d20 d6 d12 d6 d10 Wisdom d6 d12 d20 d4 d8 d12 Dexterity d10 d8 d4 d20 d10 d8 Constitution d12 d6 d8 d6 d20 d4 Charisma d8 d10 d12 d10 d4 d20