Fellow Tinkers, I'm making a server!

Alright, it might not come out for a while. All I have right now is a 5 page Powerpoint, and 4 pages are mostly empty. I was thinking about contests where you have to design a tool for something and then other people rate it. Or where you design a weapon from a pile of random parts and fight! Or a creeper-arena fighting game where you kill creepers and trade the gunpowder for better weapons, I have so many ideas, but there's one problem: I have no idea how to make a server. I will probably make some sample LAN worlds, but I don't know how to make one as an official server. Can anyone help?