See CMoS 8.155, 8.158–159, 8.164, 8.174 (series and editions), 15.104 (hyphenation)
In headings, capitalise the first and last words; all verbs, nouns, pronouns, adjectives and adverbs; and all prepositions and coordinate conjunctions of six or more letters.
Boats along the Mekong River
London Through the Ages
Family-Friendly Adventures in Phuket
The second and subsequent elements are capitalised unless they are articles, prepositions, or coordinating conjunctions, eg Island-Hopping not Island-hopping.
If the Product Manual or Design Manual doesn't specify a heading type, follow the above rules.
Straplines
Straplines in guidebooks should always be sentence case with an 'and' not an ampersand. 'Beyond' subheadings are also sentence case.
Note: headings within articles on lp.com take sentence case.