Things to consider when you interview the client:

Will it be on an articulating mount?
-If it is, will you be able to see behind the TV?
-Will they want HD? If so, where will the HD box go?
-If the box is to be velcroed to the back of the TV? What size tv will hide it / hold it?

Is there is a two-walled mirror behind the TV location?
-If so, will you see the back of the TV in the mirror? (this can be a huge eye-sore)

-Does the client expect THAT tv's sound to come through the ceiling speakers?
-If so, where is the head end? How will you feed audio for the tv / cable box?
-How will you choose tv sound in the speakers? Automatically upon TV power on? Will there be a keypad in the wall to select the TV sound or house music feed?

And yes, I know I used 'velcroed' as a verb.