This one is obvious to the veteran, but is a good reminder and something to absolutely consider a priority for the new installer.
Make sure you take into consideration these two major cabinet issues.
Depth and heat.
Your main concern will be fitting the a/v receiver in the cabinet so the door doesn’t hit the volume control and stay ajar. If a cabinet is being built or purchased, be sure to get the depth of the receiver and make an accomodation for the cable connections in the back. I usually push for at least 24” of depth.
Next is heat. Make sure air can flow and vent in and out! Allow components to have space where venting is available in the unit itself.
As a bonus third issue - PULL OUT RACK. There is nothing more annoying than having to lift a stack of equipment in and out of a cabinet, particularly when they are spread across a few shelves. Speck a pull out rack, try to insist on it, or charge more for the inevitable labor.
-Morgan