Straightforward and brutal.
Engage these rules ony if the character falls helplessly, having failed or been unable to make any Athletics, Dexterity or Reflex Save rolls to ease or prevent the fall.
A) Falling (or being thrown) for 5, 10, 15, 20, 25 or 30 feet incurs a damage roll of 1d2, 1d4, 1d6, 1d8, 1d10 or 1d12 damage respectivelly.
B) Falling more than 30 feet requires a Fortitude (or Death) save DC 15. The DC increases by 1 for each extra 10 feet fallen. On failure, the character is dead. On a successful save, the character is at 0 hp and dying.