Grossschreibung von Titlen, Ueberschriften in englischen Texten?

Auch wenn es spät kommt, hier die Empfehlung des CMoS:

8.165
Capitalization. In their original form (on title pages or at the head of articles or chapters) most titles appear either in capitals and lowercase, “clc” (\textsc{Like This}), or in caps and small caps, “csc” (LIKE THIS). Regardless of their original appearance, quoted titles may be capitalized either in sentence style (see 8.166) or, more commonly, in headline style (see 8.167). For capitalization of foreign titles, see 10.3.

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8.167
Headline style. The conventions of headline style, admittedly arbitrary, are governed by a mixture of aesthetics (the appearance of a title on a printed page), emphasis, and grammar. Some words are always capitalized; some are always lowercased (unless used as the first or last word in a title); others require a decision. Chicago recommends the following rules, pragmatic rather than logically rigorous but generally accepted:
(1) Always capitalize the first and last words both in titles and in subtitles and all other major words (nouns, pronouns, verbs, adjectives, adverbs, and some conjunctions—but see rule 4).
(2) Lowercase the articles the, a, and an.
(3) Lowercase prepositions, regardless of length, except when they are stressed (through in A River Runs Through It), are used adverbially or adjectivally (up in Look Up, down in Turn Down, on in The On Button, etc.), are used as conjunctions (before in Look Before You Leap, etc.), or are part of a Latin expression used adjectivally or adverbially (De Facto, In Vitro, etc.).
(4) Lowercase the conjunctions and, but, for, or, nor.
(5) Lowercase the words to and as in any grammatical function, for simplicity’s sake.
(6) Lowercase the second part of a species name, such as lucius in Esox lucius, or the part of a proper name that would be lowercased in text, such as de or von. For hyphenated terms, see 8.168–70. For words that can be used as prepositions, as adverbs, or as adjectives, consult Webster. All the following examples illustrate rule 1; the numbers in parentheses refer to rules 2–6.

Mnemonics That Work Are Better Than Rules That Don’t
Singing While You Work
A Little Learning Is a Dangerous Thing (2)
Four Theories concerning the Gospel according to Matthew (3)
Taking Down Names, Spelling Them Out, and Typing Them Up (3, 4)
Tired but Happy (4)
The Editor as Anonymous Assistant (5)
From Homo erectus to Homo sapiens: A Brief History (3, 5, 6)
Sitting on the Floor in an Empty Room, but Turn On, Tune In, and Enjoy (3)
Traveling with Fido, but A Good Dog to Travel With (3, 5)
Voting for the Bond Issue, but Voting For and Against the Bond Issue (3)
Ten Hectares per Capita, but Landownership and Per Capita Income (3)
Progress in In Vitro Fertilization (3)

If you are not sure what grammatical function a word is performing (or even if you are), try reading the title aloud: if you would stress the word, capitalize it; if not, lowercase it.

Lektoren ignorieren Hinweise auf dieses Manual (oder den Oxford Style Guide für Satz britisch-englischer Texte) gerne – besonders dann, wenn es um das immer noch weit verbreitete doppelte Leerzeichen nach dem Satzende geht.