Use the brand new TrueSkill™ Matchmaking system to play against opponents with similar skills, personalities, and gaming tastes.
Or, in my experience doing online vocal competition in Rock Band:
Use the brand new TrueSkill™ Matchmaking system to play against opponents who have less than one-thirtieth of your own TrueSkill score even after they quit half-way through your prior match and you marked their profile "avoid this player."
To my experience, TrueSkill = Random.
Stephen "Blue" Heaslip
Blue's News Publisher, Editor-in-Chief, El Presidente for Life