Hello, I am going to show you how to set up your own server in Minecraft.
Step 1: First Get the Software.
First, you need to get the software for the server from http://www.minecraft.net/download/ .
Step 2: Setting Yourself As an Op
To be able to use console commands, you need to set yourself as an "op" (operator(I think)). To do this, put the Minecraft_Server.exe program into it's own folder, and run it. Once it displays "Done!", you can close it. You will notice that there are more files in that folder. Open the text file "ops.txt", and type your Minecraft username. (Josh1324, Notch, ect.) For each new "op" you add, you need to put it on a new line.
Step 3: Editing the Settings on Your Server
First, open server.properties WITH NOTEPAD (or similar program). To make it so it will spawn monsters change
"spawn-monsters=false" to "spawn-monsters=true". Besides that, there wont be really anything else you will do here.
Step 4: Now You Have to Find Your Ip.
To find your ip adress, go here: http://www.whatsmyip.org/
Step 5: Fowarding the Port
Right now, you could open up the minecraft_server.exe program and run minecraft and just type "localhost" in multiplayer. But, if you want to have other people on your server, you need to foward the port. Here is a tutorial of how to do it: http://www.minecraftforum.net/topic/554-how-to-port-forward-your-minecraft-server-with-pictures/page__p__5310#entry5310
Step 6: Done!
You're done! Enjoy your server!
***You need to have minecraft_server.exe running to connect to your server!