This isn't really related to a specific class, but rather most classes can make use of a spam key to use the best available spells/abilities when it is pushed out of a selection of spells/abilities.
Since I am right handed, I use the ` key for my spam key. That leaves my right hand to use the mouse and click, etc while using my left to hit the spam key. I still have the option to click special abilities that I don't want used in a normal rotation (like dicho or dots for example).
The concept on this is to make use of your best spell when it is available.
Any questions, please let me know.