It depens on what kind of server are you making. A public server or a private server? A Bukkit server or a vanilla server? Do you wanna pay for a host or you wanna host it on your computer? I don't recommend you hosting a public server on your pc because your internet speed might not be fast enough, you might get DDoSed by hackers. And it might slow down your internet speed and computer.
Vanilla ServerIf you wanted to host a simple private server on your computer just go to
minecraft.net. Hit download, then click on minecraft_server.1.7.4.jar. Double-click the file and it should make a server by itself. Make sure you have java installed.
Bukkit ServerIf you are interested setting up a Bukkit server, download CraftBukkit from here
http://dl.bukkit.org/downloads/craftbukkit/. Replace minecraft_server.1.7.4.jar with the download. After that rename the download to craftbukkit then open a notepad and enter these lines of text "java -Xmx1024M -jar craftbukkit.jar -o true
PAUSE". Save it as run.bat and put it in your server folder. Double click run.bat and it should create a bukkit server by itself. You may add plugins into the plugins folder.
Server ConnectionYou need to set up an internet connection to let people play on your server. If you are playing with your friends, you can try getting LogMeIn Hamachi
https://secure.logmein.com/products/hamachi/download.aspx. Create a network and tell ur friends to join ur network. Then tell them enter your Hamachi IP address. But if there's more than 5 players then you need to do part forwarding
http://portforward.com/english/routers/port_forwarding/ which require a router to do it.
