20 points for first
18 for second
16 for third
14 for fourth
Then 13,12,11,10,9,8,7,6,5,4,3,2,1,0 respectively after that.

Then 1 bonus point for every car you beat that took the start.
Count your best 10 finishes. In the event if a tie you add your 11th finish then 12 and so on till a winner is decided. It is highly unlikely but possible to still have a tie, at that point they thumb wrestle at the banquet.

Stephen