A manual for writers of research papers, theses, and dissertations, 7th edition - Kate L. Turabian 2007

Talk to reference librarians
Finding useful sources
Part I. Research and writing: from planning to production

If you don't know how to find what you need, ask a librarian. Most college libraries offer tours of reference rooms and special collections, and short seminars on how to search the catalog, databases, and other sources of information. If you're a new researcher, seize every opportunity to learn online search techniques in your field.

You can also talk to librarians who specialize in your area. They won't find sources for you, but they will help you look for them. If you have a research question, share it: I'm looking for data on X because I want to find out. . . . If you have a working hypothesis and reasons, share them too: I'm looking for data to show Y [your reason] because I want to claim Z [your hypothesis]. Rehearse your questions to avoid wasting your time and theirs.