Weatherstrip and caulk all cracks between the wall and the window trim, especially under the window sills. Replace broken glass and putty any loose window panes. Caulk around the moving parts of windows with a strip-away, non-permanent caulk during the winter. This type caulk can be removed easily in the spring.
You should inspect your roof at least once a year. Nothing beats getting up close, but a good pair of binoculars can give you the next best thing. Look for curling or buckling shingles, shingle granules in your gutters, and other signs of wear.