connect [IP address here]
To clients to join a server, use: connect <ip>:<port> (for example, connect 192.168.1.1).
cmd2 jointeam 2
sv_cheats 1; achievement_reset L4D_ACHIEVEMENT_INCAP_AFTER_SAFEROOM; sv_cheats 0
Enable developer console (~)
A CFG is a file that contains a list of commands that when run will attempt to execute them all
Open up a text editor such as notepad and type in all the commands you want separating each with a ;
When done save the file as filename.cfg in <path-to-game>\left4dead\cfg. To run the cfg file, open the console during the game and type in exec filename.cfg
If you want the CFG file to run automatically, name it autoexec.cfg.
Since Split-screen mode in Left 4 Dead isn't officially supported, there are multiple important key settings which aren't immediately available.
-w X -h Y
-w 1920 -h 1080