There are 3 ways to score.
1. Capture your opponent's ball(s) in a triangle formed by your balls (+3 pts for each ball captured)
2. Knock an opponent's ball out of the square (+1 pt for each ball knocked out)
3. In the case that neither player has captured an opponent's ball in a triangle, the player with the most balls inside the square earns 1 point for each of their balls in the square MINUS 1 point for each of their opponent's balls in the square. If both players have the same number of balls in the square no points are scored by either player. (remember this is only in the case that neither player captured an opponents ball in the their triangle)
Note:
This has been updated. Years ago the original rules were somewhat different but Jake and I have simplified the rules and greatly improved our enjoyment of the game.