[Sorontar]

You and a mate can play using a single player world over a LAN or using a multiplayer world using server.

Single player LAN

1. One of you start playing a single player world in the setting you both want.
2. Set the game option to make the world "Open to LAN"
3. Have the other player chose the LAN world through the multiplayer menu of worlds.
4. The first player must keep playing to keep the LAN link active. If they leave the world, the LAN connection will shutdown.

Multiplayer server

1. One player needs to run a Minecraft server program. Mojang provide one from the same source as Minecraft. Another option is Craftbukkit ( Get Bukkit ) ,which is what we use for our Frontier and Sanctuary worlds because it is easy to add Bukkit plugins.
2. List both you and your friend in the white-list and activate the white-list in the server.properties.
3. Change any further aspects of the server.properties to define the type of setting you want.
4. Make the port that the server uses accessible to the net. Hamachi is one option to this. Using a commercial server host is another.
5. The server will run without anyone actually playing on it.

Hope that helps


Sorontar