Sometimes they become two words:
tourist guide (noun)
travel agent (noun)

Sometimes they become hyphenated:
low-paid (adjective)
film-goer (noun)

Note: There are no hard and fast rules about which category each compound word goes into but a good dictionary will tell you. You can also help yourself by making a note of new compound words you come across and the category they go into.

Generally the stress is on the first word:
phone box (noun)
smoke-free (adjective)
spoon-feed (verb)