Hi The French,
I´ve found these rules. I hope they help.
There are single-accented compounds that take the accent on the first element:
_The largest group is formed by the combination of two nouns:
a)The second noun indicates the performer of the action, as in:
baby-sitter, book-seller, car-dealer, vacuum cleaner, bartender, housekeeper, etc.
b)The first noun delimits the meaning of the second, by stating “What type of thing” it is:
school-days, bed-clothes, air-craft, time-bomb, newsagent, waterfall, etc.
_Another important group is formed by the combination of adjectives and nouns.
Normally when a noun is preceded by an adjective, both are accented:
blackberry, grandchild, secondary school, folk music, greengrocer, dark room, steering-wheel, parking zone, etc.
_Verbs and nouns sometimes combine, as in:
catchword, cookbook, pickpocket, cork-screw, fire-escape, pushchair, etc.
There are double-accented compounds that take the primary accent on the second element:
_One group is made of nouns:
a)The first noun indicates the position of the second one, as in:
country-house, camp-bed, shop window, kitchen cupboard, etc.
b)The second is made of the first one, as in:
apple sauce, olive oil, cotton wool, fruit salad, etc.
c)Other common noun + noun compounds are:
woman driver, fellow-citizen, city centre, mother tongue, ground floor, mass media, etc.
_Some common double-accented compounds formed by nouns and adjectives are:
a)Adjective + noun:
civil war, best man, prime minister, wet blanket, sliding door, common sense, best-seller, etc.
b)Noun + adjective:
navy blue, snow-white, world-wide, rent free, stone-deaf, etc.
_Participles make up some common compounds, e.g.:
air-conditioning, high-minded, home-made, good-looking, old-fashioned, easy-going, deep-frozen, etc.