Better sentence-writing in 30 minutes a day - Dianna Campbell 1995

Avoiding his or her when possible
Pronoun problems
Revising at the word level

Sometimes it’s better to change a noun than a pronoun. This is especially true if not changing the noun antecedent forces you to overuse an expression such as he or she or his or her. Sometimes it’s unavoidable, and you have to use he or she (unless you prefer he or she alone). But most of the time, this awkward option can be avoided by making the antecedent noun plural. For example, it’s acceptable to write, “A student should think seriously about his or her real interests,” but it’s preferable to write, “Students should think seriously about their real interests.”