I played on Private Servers and even ran one myself after I quit the real WoW. They are very fun at first but if you choose a Funserver that has like ridiculous rates like x100 exp or something and like x50 gold...It gets boring really fast. They do have "Blizz-like" servers in which have the same rates as the real WoW, but most of them are really empty...Same with the Funservers.
It's actually pretty easy to set it up to play on a Private Server..You just need to download World of Warcraft from worldofwarcraft.com then find a Private Server of your choice...They'll usually have a place you can register your name for the server and such..Then you'll have to go into your World of warcraft folder and find a wordpad or notepad file called "Realmlist.wtf" (Yes, it has wtf at the end...But it's real..). Then once your inside that file, you'll have to edit one of the lines to the Private Servers IP. Then it's as simple as starting the game up..