Step 1: BaselineEdit
The baseline ability score is 9. If you spend no points on an ability score, and don't have a racial adjustment, that ability will be a 9.
Step 2: The Point-BuyEdit
Next, all players will have 33 points that they can spend on ability scores. The purchase cost of ability score points is 1-to-1 up to a 13. Ability scores of 14 and 15 cost 2 points per ability score point, and 16 and 17 cost 3 points per ability score point. No ability score may be bought higher than a 17. I.E. to get an ability score up from 9 to 17 would cost 14 of your 33 points. Expensive, but possible for a specialized character. Luck is rolled normally (1d20, reroll anything less than 5).
Step 3: The Die-BuyEdit
After a player has spent all of his or her points, they all get a second pool of points. This pool equals 2 + the character's Luck bonus. These points may be spent to buy a bonus die for an ability score. The costs are 1 point for a d4, 3 points for a d6, and 5 points for a d8. In essence, you buy that die, roll it, and add that to your ability score after your purchases from step 2. You can do this up to once per ability score (Luck not included) or until you run out of points.
Thus it is possible to have a starting ability score of anywhere between 6 (9 with a -3 racial penalty) and 27 (point-buy up to 17+8 from a purchased d8+2 racial bonus), while averages will be between 12 and 16.