To start to find out what version is your copy. To do this, run the game, call the console by pressing "e" ( if the console doesn't open, then go to the keyboard settings and turn the console on). After the console opens, type into it the word version. The same is done and your companions on the game. Remember: your game version must be the same.
The next step you and your friends need to patch Left4Dead to version or To do this, first download the patch at this link (optional to take the patch on this link, you can find it yourself). Then download a pirated Steam client called SteamUP in this link Install this program and, if necessary, to register.
Then download one more program Garena — platform for games that allows you to create a local network. You can get it on this link After downloading, install the program and run it. When prompted to register by entering your details: username, password and real email address (you will receive an email confirmation).
After all the manipulations with the installation and registration of necessary programs first, run SteamUp and then Garena. In the last select Left4Dead. There will be several playrooms, from the list which the find Russian and go to her, making the standard two mouse clicks. After that open Garena setup games Left4Dead (the same button is under the chat), where in the first field, specify the path to the folder with the game, but rather to the file with the extension .exe. In the second field enter this line:

+sv_allow_lobby_connect_only 0 +sv_lan 1
After saving the settings, click "start!" in Garena, thereby launching the game. In multiplayer menu look for the line "Local server" and choose any address.