This is more of a reminder of how not to use hyphens. For the complete rules and explanations on hyphenation,
see Chicago Manual of Style (16th edition) section 7.85.
The first step is to know your parts of speech. Evaluate each word in a sentence to determine whether it's a noun, verb, adjective, adverb, conjunction, or preposition. Knowing the part of speech will guide you in whether to hyphenate.
Don't forget to warm-up.
This book is very well-written.
He is five-years-old.
The banana muffins are fat-free.
He is the White House chief-of-staff.
She is the editor-in-chief of Vogue.
Don't forget to warm up. [Compound verb consisting of verb + preposition: no hyphen.]
Don't forget to do a warm-up. [Compound noun consisting of adjective + preposition: hyphen.]
This book is well written. [Predicate adjective with no noun following it: no hyphen.]
This is a well-written book. [Adjective before the noun it modifies: hyphen.]
He is five years old. [Predicate adjective: no hyphens]
He is a five-year-old. [Compound noun: hyphens.]
He is a five-year-old boy. [Compound adjective before noun: hyphens.]
The banana muffins are fat free. [Predicate adjective with no noun following it: no hyphen.]
He is the White House chief of staff. [Compound noun consisting of noun + preposition + noun: no hyphens.]
She is the editor in chief of Vogue. [Same reasoning as previous explanation.]