We don't have a whole lot of central air here. We do have lots of forced air furnaces. I always open up the blower motor door to check the filter condition and take a look at the motor and belts (if present on the older ones). There isn't a whole lot more you can check on the motor other than is it working. I guess if it was completely full of dirt and crap you might make a note to clean it out inside there, but most of them aren't very dirty, since the dirt would be pulled into the duct by the fan eventually and end up on your TV screen.

I'm assuming that this is the motor you are talking about. They're pretty easy to replace in most situations.

I do not normally open the air handler door to look at the A frame unit. Do most of you open that door to look inside? I have opened some of them, but so many are taped closed to seal up the air leaks that I stopped because I didn't want to have to tape or reseal everything.