Also you will need to decide what kind of server you want to run. Here are 3 of the most popular.
Vanilla
Basic Minecraft, easy to maintain, but very hard to protect from griefing and cheating.
Bukkit
Minecraft but with plugins. This means that you will be able to add protection to your chests or world if you need to, make life easier with simpler commands, and give you access to many many other features. This kind of server is probably the most popular, however it takes up more RAM, and more CPU usage to run it. It will also mean it will take you some time to get to grips adding and removing plugins, and also configuring them. Its not that hard, but it will take some time if you've never done it before
And thirdly.. TEKKIT.
This is the kind of server I run. Not only will it accept plugins, but also comes packed with built in mods both server and client side. This kind of server will take even more RAM and CPU to run smoothly, but adds new blocks, machines, ores.. and in my opinion, is how Minecraft should be played