Grammatically Correct: The writer's essential guide to punctuation ...

STYLE
The clinician can play an important role on the research team. He or she
is invaluable in gathering physical data from his or her patients, and
equally useful is his or her role in gathering subjective data based on his
or her impressions and feelings.
There isn't a "magic number" of how often is too often for these
expressions; certainly, a few appearances in a large document is
unintrusive. If the need arises frequently, however, it is best to vary
he or she with other strategies.
Note: Some writers like to vary this expression as she or he, and
there is no logical reason why the female pronoun shouldn't come
first. Realistically though, since this phrasing isn't standard, it is
likely to cause momentary distraction or annoyance on the part of
some of your readers. If you recognize and accept that, then by all
means go with the variation! Perhaps if enough people do, it will
eventually become standard as well.
ALTERNATING HE AND SHE
In some genres of writing it works well to change about half the
occurrences of he to she. This strategy can be applied to made-up
scenarios or case histories, where the reference is to a single individual
and a female example would fit in just as naturally as a male
one.
It works less well if the reference is to a group or population. For
example, in the following, it would be difficult for readers to assume
that men are included:
The survey indicated that the average newspaper reader prefers her
news in a concise form.
Every worker we spoke to says that she fears for her future and that of
her family.
USING THE PLURAL
Going with the plural form instead of the singular is a simple and
effective strategy if the context is in fact referring to more than one
person. For example:
INSTEAD OF: We asked each participant to speak openly about his
feelings.
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