When I swapped form Mage to war in a pinch due to a MT going MIA I was LOST! There was debuffs, cd's both of and deff to rememebr etc etc. i was basically a lost puppy trying to find his way home and the one thing that helped me out with all the cd management and making sure I was doing the proper rotation was setting up Raven.
to this day my UI is composed of 3 custom bars that save me all teh time 1) Deff CD's up 2) priority system rotation bar 3) Offensive CD bar.
As you can see here even for some one totaly new to the class / spec you would be able to see what you had to cast next and all you woudl need to learn is the key binds :
So like many have said get a UI that helps you out > trying to memorize it