Same as @ghdprentice
Also, inside receptacles, if you suspect an issue, use Deoxit on a lint free swab like these (link 1 or link 2) that are available in different sizes. Turn power off first.
Finally, for really corroded, inaccessible internal connections (switches, etc.), one manufacturer I know uses a good spray of D-series Deoxit (although other contact cleaners probably work too). Let it completely dry b4 using.
After trying a few over the years, I use no final coatings stronger or thicker than Deoxit G100L (Pro Gold).

