You do not need tools for this walk-through, and you do not open the panel. Stand in front of it with the cover closed, and look and listen. The aim is to write down what you notice, so an electrician can see it when they arrive.
Check the cover and the wall around it for discoloration, browning, or a smell that is not dust or hot paint. Listen for a buzz or crackle when the house is quiet, and again when a large load starts, such as an air conditioner compressor or a dryer. Note which room you were in and what was running.
Look at the breakers from the outside only if the cover is clear. Note any breaker that feels warm to the touch while a room is in use, any breaker that will not stay set, and any breaker that trips only when another appliance starts. Those are the entries worth logging.
What to write down. Record the room, the appliance running, the time of day, what you heard or smelled, and a photo of any discoloration taken from a safe distance. Add the install year of the panel if you know it.
What to ask. When the electrician comes, ask whether the connections were checked for looseness, whether the panel rating matches the service you have, whether any circuit carries more than its wire allows, and whether any added breakers are the correct type. Ask for the findings in writing.
What not to do. Do not remove the cover, do not keep resetting a breaker that trips, and do not try to tighten a connection yourself. If you smell burning or see scorching, leave the area, cut power at the main if it is safe to do so, and call a licensed electrician or your utility's emergency line.
Treat the install year as a planning input. Keep it on the same sheet. An older panel is not a problem by itself, but the age tells the electrician what to look for. The electrical panel page on this site lists typical service life and planning notes.