If in doubt, check a dictionary or other reference work relevant to your particular topic. Dictionaries are particularly useful to see whether a word has become common enough to be set solid.
Caution! Entries in some dictionaries are based on use in the community. This means that compound words that look similar may be set inconsistently (eg in the Macquarie dictionary, policymaker is one word, and decision-maker is hyphenated). If you have words like these in your text, you will need to decide whether to follow the dictionary or to present them in the same way (eg both solid or both open; either is acceptable) so the text is consistent.
