Avoid using masculine pronouns to refer to both men and women.
If you know the chair of a committee is a man, then it’s OK to use chairman. Likewise, if you know the chair is a woman, you may use chairwoman. But if you don’t know the gender, use chair (not chairperson). It’s OK to use mankind, humanity, or manmade, because these words don’t presume one gender or another.
Try not to resort to “his/her” constructions. Do not use the plural pronoun “their” in an attempt to be gender-neutral when a singular pronoun is called for. Usually the best strategy is to reword the sentence so that you can use the plural pronoun. Instead of saying "Every swimmer is responsible for providing his or her counter" try "All swimmers are responsible for providing their own counters."