Terms that are used as adjectives should be hyphenated. Hyphens are used in compound adjectives.
Examples include:

• cutting-edge technology
• high-level overview
• off-the-shelf software
• 24-hour turnaround
• full-time job
• part-time staff
• short-term plan
• long-term strategy
• two-day conference.

Use when both prefixes modify the same word.
Examples include:

• short- and long-term
• sisters- and brothers-in-law
• three- and four-digit numbers.

Use hyphens to connect numbers defining ages coupled with the words year-old. For example, 25-year-old, 25- to 75-year-olds.

Hyphens should be used to clarify the meaning of words. For example, when the last letter of a single-syllable prefix is a vowel and the word that follows begins with the same vowel. For example, de-emphasise, pre-eminent, re-enter. This is less crucial if the word is well known. Do not hyphenate cooperate and coordinate.

Use a hyphen to distinguish new words with prefixes from established words that would otherwise look the same.

Use a hyphen with co- and ex- prefixes. For example, co-author, co-worker, ex-alderman, ex-wife.
There are instances in which compound words (words made up of two separate words) should be left without a hyphen:

• Those consisting of an adverb ending in ly followed by a participle or adjective, for example: frequently used method, highly regarded teacher.
• Compounds with a modifier, such as very, for example: very fast runner.
• Compounds with comparatives or superlatives, for example: more recognised practices, better known stories, less able students.
• Compounds comprising two nouns, or an adjective and a noun, followed by a noun, for example: equal employment opportunity, senior schooling report.

There are instances where compound words should be hyphenated:

• When the meaning may be ambiguous, for example: the 15-odd members of the P & C, not the 15 odd members of the P & C.
• When the word looks strange when closed up, for example: anti-inflationary, anti-Semite.
• When it comprises an adjective or noun and a participle, for example: all-encompassing, left-handed, full-grown, state-owned.
• When it comprises an adverb and a participle, but only when the expression is used attributively, for example: a well-known children's book but a children's book that is well known.
• When the second component consists of more than one word, for example: non-English-speaking.
• When one of the prefixes stands alone, for example: macro- and micro-economics.

Hyphenate words containing:

• great (great-grandparent)
• vice (vice-president)
• ex (ex-teacher)
• self (self-esteem)
• elect (mayor-elect)
• odd (thirty-odd, twelve-hundred-odd)
• all (all-seeing, all-important)
• most words containing half (half-term, half-hourly, half-measure)
• many words beginning with cross (cross-country, cross-examine, cross-index)
• semi followed by a word beginning with i (semi-isolated)
• most words beginning with non (non-academic, non-hereditary, non-state school; exceptions: nonverbal, nonfiction).