Use gender-neutral language (e.g. “firefighter” rather than “fireman”).
Do not use masculine pronouns to refer to people generally:
Wrong: A good actor will follow his own instincts. [The sentence implies that only men can be good actors.]
Technically wrong through frequently heard: A good actor will follow their own instincts. [Technically, the use of “their” produces a noun-pronoun agreement error. Many people think that English needs to develop a gender-neutral singular pronoun. See AGR n-pr.]
Awkward: A good actor will follow his or her own instincts.
Better: Good actors will follow their own instincts. [Plurals are a good solution because plural pronouns are gender-neutral in English.]
Better: A good actor will trust personal instinct. [The personal pronoun isn’t always necessary. Leaving it out solves the problem.]
The adjectives “masculine” and “feminine” pertain to gender (a cultural distinction), while “male” and “female” pertain to sex (a biological distinction).
Use the nouns “men” and “women” rather than “males” and “females.” The latter terms refer to animal populations.
Even idiomatic expressions like “the fall of man” are best avoided or rephrased.