What is the rule for neutral gender as antecedents?

A neutral gender noun, also called a common gender noun (for example doctor, parent, driver, etc.) has no specific rule for a pronoun to take its place.

Sometimes the pronouns 'they' and 'them' are used even for a singular antecedant; sometimes an indefinite pronoun is used, for example 'one' or 'each'. Sometimes the default 'he' and 'him' is used when speaking, or some people use the clumsy 's/he' or 'he/she' when writing.

The pronouns that take the place of a neutral (common) gender noun depend on the context of a sentence or the preference of the speaker (writer). When the gender of the person is known, the specific male or female pronoun can be used; for example:

My lawyer told me that she had filed my case.

Our neighbor said that he would cut our lawn.