Use a conditioner when washing your hair. But most people already do that, so...
...some clothing fibers are prone to generating static (polyester, rayon, coarse wool). Do not use a plastic toothed/bristled comb or brush... these are major culprits and those are bad for your hair anyway. Limit the amount of time you let your hair hang loose.
Also... do you drag your feet when you walk? In drier weather, it will make an impact on how static-y you become throughout the day.