At one time I had an AHS home warranty, but dropped it when I read that they tended to not cover if you failed to perform the smallest maintenance tasks. That said, reading the list of tasks that people got denied for did raise my awareness on a few pieces of maintenance I wasn't doing as consistently as I should.

What regular home maintenance tasks are really worth the effort for reduced appliance or structure failures?

Please post one suggestion per answer to let people vote up and discuss.