Due to variations in disciplines and the preferences of publishers, there are many more style guides available than the usual MLA/APA/CMOS. This guide serves as an introduction to how to format your document as well as provides examples of the most common citations only.
We recommend sticking with one of the big three styles (MLA, APA, CMOS) for lower-division undergraduates for the sake of simplicity: there's no reason to struggle with learning a specialized style that they're unlikely to ever encounter again (or only encounter as a graduate student of that discipline). If you feel it necessary to use an unusual style, please adhere strictly to the style guide without interjecting elements of MLA or another style, as the relatively limited resources for these styles already makes them more difficult for us to support.
DOI = Digital Object Identifier
Use a DOI (if assigned to the article) when citing articles, whether accessed in the print or electronic form.
A DOI is a digital object identifier – a unique alphanumeric code that gives a persistent link to the web location for an electronic item, sort of like an ISBN. DOIs are commonly seen on current electronic journal articles, but are often also included in the print version of the article. You're more likely to see them on articles for the sciences than the humanities.
A Digital Object Identifier (DOI) is preferable to a Uniform Resource Locator (URL) when citing an online resource.