Cshmid: Fair enough. There are a myriad of things to look for behind a panelboard cover. The short list would look like this:
(1) Before the cover comes off - are the breakers labeled? Are there openings in the panel cover? Are all of the cover plate screws in place, and are they the blunt-ended screw supplied by the manufacturer or are they sharp-pointed sheet metal screws installed by the Sparky or happy homeowner? Is there the required service clearance around the panel? Is it installed at a code-compliant height? Is it installed the proper distance from propane tanks? Is it located too close to a gas appliance vent? Etc., etc., ad infinitum . . .
(2) Are any of the breakers overheating - using an infrared thermometer for measurements.
(3) Are there any damaged breakers?
(4) Are there any scorch marks?
(5) Is the panel full of crap like mice nesting material, dead mice, paint, texture, et al.?
(6) Are the conductors sized properly for the breakers to which they are attached?
(7) Are all of the conductors connected to the panel where they enter with NM clamps?
(8) Is there the proper amount of cable insulation extended within the panel?
(9) Are any of the conductors damaged?
(10) If aluminum, are the conductors attached to breakers listed and labeled for aluminum? Are the bare ends coated with anti-oxidant paste?
(11) Are any of the breakers being used to protect more than one circuit? If so, are the breakers listed and labeled for this application? Are they properly sized according to the circuits they protect?
(12) How many conductors are inserted below each lug in the common and ground bus bars?
(13) If this is a subpanel, are the commons and ground segregated?
(14) Is this a POS panelboard like a Federal Pacific Electric Stab Lok or Zinsco. You know the ones I mean, arc welders in a can?
(15) Are breaker handle bridges in place where required?
(16) Are all of the breakers in the panel of the brand or type allowed for installation in the panel?
(17) Are any of the breakers on a UL or manufacturer recall list?
(18) Is the enclosure rusted? If so, what is the origin of the moisture?
(19) Are there any devices in the panel that do not belong, i.e. doorbell transformers, whole house surge protectors, et al.?
I could go on, bu these are what come to mind right now. Gotta run . . . the brisket needs basting . . .