Mount it away from the corners of the room.
This is a must to consider because of low frequency feedback. A corner can be a bass trap. This happened with my wall shelf and it was a pain to get rid of.
Advice for mounting a TT shelf on a wall
For more than one reason, I have decided to place my TT on a wall shelf. Now it occurred to me that there may be preferable places on the wall for the shelf to be mounted. Taking into account standing waves, electrical interference (hum), and even height, I suppose that one location is preferable to another.
Also, this is a very heavy duty shelf, and there may be additional considerations just because of this. No doubt, I will locate wall studs for mounting. What considerations come to mind for this?