you get as much points as your finish place is ( i think not finishing = last place ).
the points get added until 3 races pass by, so there is always sum of your last 3 races points.
player with least points is in 1st grid 1st pos, with 2nd least 2nd pos in 1st grid, and so on...
when grid gets full new one is created.
guests are placed randomly in back i think