You were probably taught to cite modern works of scholarship by title or author and page number. For example, if you are quoting, paraphrasing, or referring to Duckworth's discussion of the "running slave" scene, you might write:
... Duckworth lists "the excessive haste of the running slave" as one of the varieties of "exaggerated and farcicial action" in Roman comedy (Duckworth, p. 324).
This would correspond to a full citation for Duckworth's book, normally in a "bibliography" appended to your paper:
Duckworth, George E. The Nature of Roman Comedy: A Study in Popular Entertainment. Norman: University of Oklahoma Press, 1952.
Ancient sources are cited much more precisely than modern ones. To cite an ancient text in prose (a speech by Cicero or Demosthenes, a philosophical work by Plato or Aristotle, a historical work by Livy or Thucydides, and so on), use the conventional book, chapter, and section numbers. These numbers are not ancient -- Cicero and Plato did not divide up their own texts this way -- but they are standard, and have been used for hundreds of years to refer to these texts. For example,
Cicero in his speech For Marcus Caelius compares the arrest of Licinius to a scene from a comedy (Cic. Cael. 65)
To cite an ancient text in verse, give the book, if there is one, and the line number. All ancient plays are in verse, as are epics and lyric poems. For example,
Euelpides finds the Hoopoe's appearance so bizarre that he asks whether he is a normal bird or a peacock (Birds, 102).
Sometimes a translation of a verse text will follow the original line numbering, but more often the translator will use more or fewer lines (usually more) to say the same thing as the original. You should always cite using the line numbers of the original Greek or Latin text, not the translation.
Some prose texts, particularly the works of Plato, Aristotle, and Plutarch, have section numbers that correspond to pages in a particular early modern edition; they will not start at 1, and they will not match the logical divisions of the text.
Put brief citations directly into your text, in parentheses, as shown in the examples here. Do not use footnotes; in classical scholarship, footnotes are generally only used for side arguments, not merely for citations.
In your bibliography, give a proper citation for every edition or translation you consult, including the name of the editor or translator as well as that of the ancient author.
The same scholarly standards apply to on-line texts as to printed ones. You must evaluate on-line sources as carefully and critically as books. Just as you would not cite a comic book or, say, People magazine in a scholarly paper, so, similarly, you should not cite frivolous or popularizing web sites. Once you determine that material is appropriate for the use you wish to make of it, you must cite fully enough that interested readers can find the text you used and draw their own conclusions from it. A full citation for an on-line source always includes the title, the name of the author or editor, the URL, and the date of access.
General encyclopedias, as a rule, are not cited in scholarly work. This applies both to print and to on-line encyclopedias. While Wikipedia, Encyclopaedia Britannica, Encyclopedia Americana, and so on are perfectly reasonable places for you to look for basic background, they are not scholarly works and they do not take the place of work with primary texts and the research literature.
Specialized classical encyclopedias may be cited. These include The New Pauly and the Oxford Classical Dictionary.
When you cite a text from the Perseus Digital Library, give the ancient author, the title, and the
name of the editor or translator, just as you would for a printed text, then give the URL. For the classical texts
in Perseus, the preferred URL for citation is the one displayed at the bottom of the page, which is not necessarily
the same as the URL displayed by your browser.
When you cite other materials from Perseus, give the author or editor and title for credited works (including catalog entries and photographs), and give the URL.
When you cite other on-line sources, be sure to determine the author of the page you are citing as well as its title. Any text that is suitable for scholarly work will have a known author. If you cannot find the author of the page or site you are looking at, it is probably not suitable for citation.