For the most part citations of ancient works begin with the author's name (sometimes abbreviated), followed by a short or abbreviated title, usually in italics. (In cases when only one work by an author is known, the title is often omitted.) This is followed by a sequence of numbers and/or letters that indicate the specific subdivisions of the work. Exactly how works are subdivided varies. Book, chapter, and/or line numbers are often provided. Some works are cited by page numbers of standard, or once-standard, editions. Scholarly editions of these texts will be subdivided by these schemes, as will many translations.
For more information see the Chicago Manual of Style, 15th edition (Chicago, 2003). See also The SBL Handbook of Style For Ancient Near Eastern, Biblical, and Early Christian Studies (Peabody, MA, 1999), §8.3.14.
Abbreviations should be taken from an authoritative source, such as the Oxford Classical Dictionary (see below). You should also provide bibliographic details of the edition and/or translation of the work you are using: generally when the work first appears in your notes and in your bibliography.
Some additional points
The abbreviations of journal titles in classical studies and related fields found in the Oxford Classical Dictionary and L'Année philologique are widely used. For abbreviations not found in these sources, check Wellington's Dictionary of bibliographic abbreviations. For archaeological periodicals see the abbreviations used by the American journal of archaeology.