The MLA Handbook (9th ed.) differentiates between core and supplemental elements. Core elements are generally included in a citation, as long as you can find the relevant information. Supplemental elements are sometimes important and sometimes optional. They are placed either after the title of the source or at the end of the entry.
Place an important contributor to the main work after the title, and before the container:
Berlusconi, Lucia. “An Italian Girl in Provence.” Translated by Robert Mayle. The Best Travel Fiction of 2021, edited by Edmund Grumperlinck, Gourmand Publishing, 2021, pp. 99-105.
In this case, the contributer (Robert Mayle) translated this particular story, but did not necessarily contribute to the rest of the book.
In some cases you may want to provide the original publication date. This information also comes right after the title and before the first container:
Lively, William. The Spanish Comedy. 1598. Edited by Karen Sondheim, Oxbridge UP, 2014.
If you want to show where something has previously been published, use a tag (e.g., “Originally published in”):
Chuckle, Hillary. “Ventriloquizing the Belly Laugh: An Ethnographic Perspective.” Recent Essays in Ethnography, edited by Boris London, Naked Truth Press, 2008, pp. 58-72. Originally published in ROFL, 2005.
You can shorten the publication information for the original source.
For electronic sources, you may provide a date of access. This date indicates when you consulted the electronic source for your research:
Beard, Stuart. “The Final Run.” Sofa Surfers, 8 Feb. 2017, www.sofasurfers.com/stories/the-final-run/. Accessed 20 Feb. 2017.
The date of access is useful because websites change constantly. However, it is not mandatory.
For multivolume works, you normally cite only the volume you used. On the other hand, if you want to indicate the complete number of volumes in the series, you can add this at the end of the entry:
Devereux, Bob, editor. The Secret Correspondence of Elizabeth I. Essex Press, 1991. 6 vols.
When a book is part of a series, you may include the series title and/or the number of the book:
Etui, Alice. The History of the Pencil Case. Oxbridge UP, 2016. Culture, Style, and Education 3.
To provide clarity, you may sometimes want to give a brief description at the end:
Flytrap, Venus. “The Science behind Trigger Warnings.” Mental Health and the Return to Nature. Peruvian Pavlovians Convention, introduced by Florence Wheelock, 3 July, 2009, Universidad Nacional Toribio Rodríguez de Mendoza de Amazonas, Chachapoyas, 2017. Presentation.
Normally, the medium of publication is not needed.
If you cite a government document, you can provide additional information:
United States, Congress, House, Committee on Oversight and Government Reform. Curtailing Presidential Tweets. Government Printing Office, 2017. 115th Congress, 2nd session, House Report 592.
For more information on supplemental elements, see chapter 5 of the MLA Handbook (9th ed.).