On the model you want to keep score of, usually your User model, put this code:

has_score

On the model that awards score put this code:

keeps_score :if => Proc.new { true },
            :on => [:create],
            :amount => Proc.new { |tc| 1 },
            :for => Proc.new {|o| o.user }

then goto /competition/leaderboard and viola!