This guide is intended to help with your upcoming projects, and thus will cover both:
This guide assumes that you already understand the basics of literary research. For more, please see:
The Aarne-Thompson-Uther Index is a system used to classify myths and folktales according to the underlying structure of the plot, themes, and motifs. It was first developed by the Finnish scholar Antti Aarne in 1910, and later expanded by Stith Thompson in 1928 and 1961; numbers referring to their work are called AT numbers. Hans-Jörg Uther further expanded the system in 2004; numbers referring to this update are called ATU numbers. The AT and ATU Indexes are used to group tales with common characteristics. Each named tale-type is assigned a number and classified within a broad category of tales:
1-299 Animal Tales
300-749 Tales of Magic
750-849 Religious Tales
850-999 Realistic Tales
1000-1199 Tales of the Stupid Ogre (Giant, Devil)
1200-1999 Anecdotes and Jokes
2000-2399 Formula Tales
Thompson's Motif-Index of Folk-Literature is often cross-referenced with the ATU Index to trace motifs across diverse tale-types.
Knowing the right ATU number can make it MUCH easier to find materials on your tale.
The University of Missouri Libraries have compiled a very useful guide to finding folktales by ATU number. Or, you can try the library resources below.
Types of the Folk Tale by 
Motif-Index of Folk-Literature, Volume 1 by Most of the sources I cite in the section are reference sources of one sort of another; their real strength is in the other sources they cite. They are very useful as starting points, not ending points.
Web Resources
Library Resources
Again -- these are resources for beginning your search! You'll need to check their bibliographies.
You might want:
Subject terms can help you. In a lot of cases, there isn't really an author's name to search as a subject heading, but you might consider using topical subject headings that can help you to find the books that establish context.
Notice that many of these are about genre, but include terms like "in literature." In most cases, these books are about how fairy tales and folktales have been adapted or used in literary works. Since most of the headings about adaptations focus on adaptation into other media (especially film) it can be hard to find useful works on adaptation more generally.
I've also included a couple more specific examples. "Witches in literature" and "Bluebeard in literature" are good examples of the kinds of searches that I can't easily predict you might do, but that may still be fruitful for you! The point is that many of the fairy tale elements may themselves be the subject of books.
The Advanced Search is especially useful when considering how these many factors may overlap. In particular, it's very useful for finding feminist criticism in a particular subject or genre. Combine a subject heading search with words like femin* or gender or women.
Authors have their own call ranges, but books on fairy tales and fantastic literature can generally be found at the call numbers:
PN 3435 - 3437
Evaluating sources is tricky! There is no one test that will tell you whether a source is a good one or not. I can, however, suggest some questions you might ask:
Is this a scholarly source? Scholarly sources are those sources written with a scholarly audience in mind. These can often be identified based on where they are published (in a journal focused on a specific field? in a book by a scholarly publisher?) and are usually characterized by their depth of analysis and their copious bibliographies. If you're not sure, check the publication or publisher.
Is this source part of a relevant conversation? "Relevant" is difficult, of course, because it depends on what you're doing rather than what the source is doing! However, there are some elements that you should consider, including recency (articles older than a couple decades are likely to be part of a different conversation), the perspective from which the author is operating, and the kinds of sources that an author cites.
Does this source make me look good or bad? When you cite a source, you're not necessarily agreeing with the author, but you are identifying the author as someone worth listening to. This means you need to stay aware of the scholarliness of a source, and where and how it was published. Sometimes students stumble on (for example) old student projects, and if they cite these projects without appearing cognizant of the difference, then it can create the appearance that they don't understand the scholarly conversation. These sources may not be without merit, but you need to show that you understand what you are looking at.
Convenience. You are an experienced and sophisticated student -- so you should choose the best sources available. You've grown beyond the point where you can expect to find everything you need available locally. Fortunately, we have Interlibrary Loan and CLICS to ensure that you can access the best scholarship whether we have it here or not -- so please avail yourself of these services if you see a source that we don't have!
Bluebeard: A Reader's Guide to the English Tradition by 
Cinderella: A Casebook by 
Fairytale in the Ancient World by 
The Greenwood Encyclopedia of Folktales and Fairy Tales by 
The Oxford Companion to Fairy Tales by 
Routledge Companion to Fairy-Tale Cultures by 
