Hyphenate two or more words when they team up to modify the noun that follows. Do not hyphenate them after the noun. A well-known rule. The rule is well known. Punctuation choices like this sit with ACT punctuation rules.
Before the noun
A last-minute registration, a 36-point scale, a full-length practice test. The hyphen tells you the words act as one adjective. Without it, a full length practice test reads like three loose words.
Skip the hyphen when the first word is an adverb ending in -ly. A carefully written essay needs no hyphen. Carefully already modifies written. Adjective and adverb jobs are in adjectives versus adverbs.
After the noun, and capitals
The registration was last minute. No hyphen once the phrase follows the verb. Proper names and titles are a different rule, in capitalization on the ACT. The grammar map is in ACT grammar rules.
The bottom line
Hyphenate the compound when it sits in front of the noun. Leave it open when it comes after.
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