Grammar

Write in the active and use the first person where necessary.

Try to avoid long sentences that have several embedded clauses.

Sex: avoid "he" as a general pronoun. Make the nouns (and pronouns) plural, then use "they"; if that's not possible, use "he or she".

Nouns and verbs should agree:

The data are; None is...

Organisations and groups of people take singular verbs:

The government is; The team has researched...

Avoid noun clusters:

"Patient in coronary care unit" rather than "coronary care unit patient."

Watch out for "danglers" (unattached participles and misrelated clauses):

Joining the service in 1933, his first post was... (the post didn't join the service)

Joining the service in 1933, he was first posted to... (this is correct)