This guide works with all WoW Private Servers !

Step 1: Go into your favorite WoW site and register an account.
Step 2: Download the client and anything you require from the WoW site of your favorite.
Step 3: open your World of Warcraft\Data\enUS\ directory and edit your to whatever it shows on your WoW Site
Step 4: Careful here you must use wow.exe to launch your gamer never launcher.exe
Step 5: Login with the account you've created in step 1

Most Private Server Sites usually have this kind of small guide on how to connecting to their servers.

*** you must only use one server at a time, putting multiple server ID's in your might cause the game to stop working. You could try changing them to switch between servers, but some servers use older or newer version of the game so it might not work.