I check the wiring in the old panel as I'm disconnecting it. If there's an unusual connection, I'll investigate. I also check visually anytime I'm in a home. Typically services here are in a basement & the wiring is exposed. If there's a problem, I'll bring it to the owners attention.
Other than that, I wouldn't typically go around the house and check polarity and voltage on outlets, if that's what you're asking.
