Back up your current UI by...

Copy or zip your current Interface folder and place it in a different area
Copy or zip your current WTF folder and place it in a different area

now..

Delete the Interface and WTF files inside your wow folder
Delete the Cache folder
Delete the Logs Folder

Place the Interface and WTF files in your World of Warcraft Root directory.

Open WTF file
Open Account folder
Rename the "AccountName" Folder to your Account name in all CAPS, this is your account name not your battle.net login
i.e. THISISMYACCOUNTNAME

Now open your account name folder that you renamed.

Copy Server folder as many times as you have servers that you play on
Rename the server folder to the name of the server

i.e. Bloodhoof , Daggerspine, Shattered Hand

open your now created server folder

copy Character folders as many times as you have characters on this realm

Rename each folder to the name of your character

i.e. Uitat, Deranjata, Iamhealz, and so on

REPEAT THIS PROCESS IN EACH SERVER

close the window

open World of Warcraft Client

enter your Details

check the addons button on character screen to see if you have the enable out of date addons checked. (only need to do this if its a few days after patch and i have not updated yet)

Log into your Character

when Asked.... select the class you are about to play, and the screen will automatically reload