In addition to using hyphens as they appear in dictionary entries, you’ll need to put hyphens between words that function together as an adjective before a noun.

a large-scale manhunt

a 17-year-long campaign of terror

When such a combination comes after the noun, do not hyphenate it unless it is likely to be misread:

a manhunt on a large scale

Avoid assembling long strings of words that need hyphens to be understandable:

a federal-government-funded crime-control initiative

a crime-control initiative funded by the federal government

Do not put a hyphen between an adverb ending in -ly and an adjective:

a federally funded initiative to control crime

a completely new problem set

Most — but not all — words that end in -ly are adverbs.