Citing Generic Unpublished Work
According to the seventh edition of the MLA Handbook for Writers of Research Papers, if your source is unpublished and doesn't have a specific citation system for that type of work, then you would use the following format to properly cite your source: Author (last name, a comma and then the first name). Document Title (italicized). Date of Composition (or n.d. for "no date"). MS or TS (indicating if it is a handwritten "manuscript" or typed "typescript"). Location of Material (Institution, Location or Collection Name or "Author's private collection").
For example: Doe, Jane. Pizza Toppings (italicized). N.d. TS. The Pizza Museum Collection.
Unpublished Work with Specific Citation Rules
Some unpublished sources have specific citation rules. For example, a personal e-mail should be cited like this:
Smith, John. "Re: Nabokov's Butterflies." Message to author. 17 May 2012. E-mail.
An unpublished thesis or dissertation also has its own citation method:
Smith, John. "Butterflies in Literature." Diss. Duke University, 2013. Print.
Always check in the style guide to see if there is a specific way to cite your source before using the generic formula for citing an unpublished source.