Good writing is clear, specific and concise.
Anyone who is writing something has to make choices. On which side of the period do I put the quotation marks? Do I capitalize the job titles of the people in my office? How do I refer to the departments within my school? There are a few reference works that will help answer your questions.
Refer to for questions related to words and their meanings. There’s a very handy online version, but only the printed edition is authoritative. Get the version you can use as a doorstop. Language is a living thing, so make sure that you use the latest edition.
The latest version is available online, via an app for your smartphone, and even in print. Check out apstylebook.com, @APStylebook and #APStyleChat on Twitter.
The Elements of Style, by William Strunk Jr. and E.B. White, is a time-tested classic guide to writing with clarity and style (but ignore their advice about using the serial comma).