ima assume ur kinda familer with hamachi (ham)
if ur not read this otherwise skip down
1. Install Hamachi on both computers (make sure u both have the same version or ur asking for trouble)
2. down the bottom somewhere is a button that looks like a triangle called new network.
3. create a network and password.. tell ur friend the password and anyone else u want to join ur games
4. Make sure both u and ur friend(s) join the network before starting the game
5. launch CS
in CS when you make the server through the "New Game" tab in Counter Strike your friend that is in your network will be able to see this game through LAN in CS. If your friend or you get an error which is somewhat like this: LAN Class Restricted. The server host has to type this in console. "sv_lan 0" After that command is typed in your are good to go! This works for most of the games.
worst case senario(aka what happened to us...)
we had to use Garena which was made for warcraft 3 but has about 2000 CS 1.6 players on it
its easier to setup and use
GL and HF
EDIT:
heres a site that did it differnetly but has pictures
http://www.hamachi-games.ic.cz/index.php?page=14