Instructions
Download and run "Minecraft_server.exe" from the "Minecraft" website. This will launch your own server.
Type "/op [playername]" in the server console to make that player an operator on your server. Replace "[playername]" with the player's user name. This is a temporary status change to the player and will be removed when he leaves the server.
Open the "ops.txt" file in the server folder and add the player's name to the list of OPs. Restart the server and that player will always be an OP until you remove his name from the "ops.txt" file.