There is nothing set in stone, other than code requirements (if applicable in your installation) and common sense. Keep in mind, this is sensitive electronic equipment that will require periodic maintenance, as well as potentially be upgraded as it ages.
The National Electrical Code sets safe working spaces and distances for headroom, as well as on each side and behind where someone working would be standing. If you are in doubt of location, reference the NEC as well as your local authority having jurisdiction (AHJ).
Some good rules of thumb would be:
Install the control panel within a protected area to avoid compromise.
Install the unit with enough space to comfortably work on it.
Install the unit with adequate light to work on it.
Install the unit in an area, which is accessible without special equipment.
Install the unit within a cool, dry area.
Install the unit using all the factory mounting holes.
Follow the manufacturer's directions for temperature rating and proper mounting methods, use proper anchoring and mounting methods and plan for additional space for expansion, upgrades, or changes.
Attics and extremely hot or humid areas.
Areas subject to flooding or moisture.
Areas exceptionally close to gas mains.
Areas directly beneath plumbing.
Mounting the unit directly on concrete without an insulator or fiber washers.
Mounting the unit in an area which may be subject to remodel or change.
Mounting the unit where it is subject to damage and compromise.
Mounting the unit outside.
The use of Velcro, double sided tape, or even caulk to mount the unit.
Normally you will see a control panel mounted in a basement, utility space or closet. At times, due to installation demands, none of these are an option, so compromises are made. Your personal installation will also dictate which locations are not suitable.