Type the following commands into the console in order to setup a server. To get the console up either press the ~ key or put -console after your shortcut or go to steam > play games > right mouse button on half life 2 > launch options > put -console there.
maxplayers (whatever you want)
map (mapname ie hl2mp2.bsp)
To connect to a multiplayer game just type:
"connect" followed by the IP address the port number is usually "27015".
Del med dine venner