Professional associations produce style guides in order to standardise citation methods in their field. These standards should be adhered to, unless there is a very good reason to use or create another style.
Below is a list of some professional association style guides. Corresponding CSL styles for most of them are at the Zotero style repository.
If you know of other official association style guides, please add them
(this is a wiki, and you are welcome to contribute).
Many style guides are in the form of books which are not freely available; your library may hold a copy, and there are also webpages like this and this which give free and simple guidelines on using the styles correctly.
The use of unique identifiers, such as the DOI, is increasingly encouraged in citation styles.