It seems like the ranking system is somewhat of a mystery.
How many points do you get for a win/loss/disconnectwin/disconnectloss?
Does the ranking of your opponent matter? Does getting Most Exciting or Most Boring (etc) earn you points?
Who knows?

Each time you win a deathmatch, fort or race you earn points with deathmatch awarding the most points. When you lose or get a disconnect you lose points. The amount of points depend on the rank of your oponnent.
For the most exiting, most boring thing that I can't answer

**When someone disconnect on you it's consider that both disconnect, however if you win the first round and the opponent disconnect you're awarded points / if he win the first round and disconnect on the second round you lose points and he gain some.

According to one of the Team17 staff, the PSP version puts 10% of each players points in the pot and the winner takes all. The DS version seems to be similar. It would take a lifetime to get on the top of the leaderboard by only playing first timers since you get hardly any points for defeating them but if you defeat someone with a high rank, your score will rocket up.