Forum:Multiplayer: More Than 1 Player on a Console?

I've seen people using one console (Xbox 360) to support 2 players in a match. Their gamertag shows up normally for the host (example360) and adds a digit for the guest (example360(1)). I'm trying to allow a friend to join me, on my Xbox, in an online game, but can't figure out how to get them onto my lobby.