Well, going off the champs in 2009, it goes roughly like this:

To start we have 3 qualifier round with three robots in each, from these qualifiers we gain points for the following
4 points for a knockout win
3 points for win by judges decision
2 points for 2nd place
1 point for 3rd place (but the robot must have entered the arena)
0 points for not entering the arena

The qualifier rounds are decided by the pre-event draw

Top ten scores from the qualifiers go through to the knockout rounds, which goes:
5 1v1 fights
5 way losers melee, 1 robot goes through

3 1v1 fights
3 way losers melee, 1 robot goes through

2 1v1 semifinals

3rd place play off

Final