If you are just getting started in a new area, you can always get there by consulting Robert Balay, et - al., Eds, Guide to Reference Books, 11th ed., (Chicago: American Library Association, 1966). Do not buy this unless you are independently wealthy; write the ALA and tell them to reduce the price and to put it on a CD-ROM.. It will be behind the reference desk in any good (almost any) library.

Another good book for getting started in a medieval area: F. A. C. Mantello and A. G. Rigg, Eds. Medieval Latin. An Introduction and Bibliographical Guide.(Washington, D. C.: Catholic University of America, 1996). Each  was section done by an expert in the field.

 If you still have Martin R. P. McGuire and Hermigild Dressler, Introduction to Medieval Studies  (Washington, D.C.: Catholic University of America, 1977) don't throw it away.

If you have a Karl Stecker translation  R. B. Palmer, Introduction to Medieval Latin , 2d ed. (Berlin, 1957), don't throw that away either. Read through it. Remember: Balay is for looking up; go to the reference desk and xerox pieces;  note that it will usually have the call nos. of the library in the margins. Keep those. The others are for browsing through. There are a number of online bibliographies. Don't complicate things at  first; stick to the MLA.

See also, Robert Earl Kaske, Medieval Christian Literary Imagery : A Guide to Interpretation. in collaboration with Arthur Groos and Michael W. Twomey. (Toronto ; Buffalo : University of Toronto Press, 1988)