Here's how the ladder works. You can also look at a simple example.

Initially, every player starts with 2000 ladder points.

For every victory, the winner gains points and the loser loses the same number of points. The better the opponent you beat, the more points you get for a victory. For example, if you beat a player who has as many points as you, you get 50 points and the losers loses 50. If you beat a player who has 100 points less than you, you only get 34 points; if you beat a stronger player who has 250 points more than you, you get 84 points. The exact curve is here:

In addition, per game played every player gains 2 points. This is a tie break so a player, say, with 6 wins and 5 losses is (on average) higher in the ladder than a player with only 1 win overall.

If a game ends in a tie, every player only gets these 2 points.

For multiplayer games, the same formula is used, but players split the reward (or penalty) baes on how many players they beat, tie and lose against in the game.

If you want to have a peek at the (ugly) machinery that computes the ladder, let me know and I'll mail you a copy of the M$ Access database with the games and the MS Excel spreadsheet I use to actually compute the ladder points.