The problem with the lobby/server system in L4D is that you only have access to players on your friends-list. Fortunately, the
TG-L4D steamgroup has over 650 members! To help take advantage of this, the L4D admin team would like to request people
form games by joining the steamgroup chat room!
(If you haven't yet,
click here to join the steamgroup)
To do this, simply go to the bottom of your friends list:

... or via the
TG-L4D page as shown below:

Instead of inviting friends to a lobby, start by inviting them to the group chat:

Once you have enough people for a game, have someone start a lobby or join the server (either via main menu/console command/server browser) and everyone else can follow them in:
