Clarify your topic or thesis. One reason for searching is to gain clarity on a research topic. And the more clarity you gain, the easier it is to search. It is an ongoing iterative process. Use a written draft of your topic as a touchstone to which you can return often to clarify and prioritize what you're searching for. Run it by your instructor or others periodically for feedback. For quick summaries of topics, try Reference Works
Keep a Search Journal. It is easy to lose track of what searches worked or didn't work. There a couple methods for tracking your search history.
Books or Articles? Unlike the sciences, the largest proportion of scholarly work in the Humanities is published in monographs (books by a single author) rather than in journal articles. Social Sciences falls somewhere in between. Use DiscoverE (primary tab) or WorldCat to find books; use DiscoverE (articles tab) or Google Scholar to find articles. Google Books often publishes sections of works still in copyright, esp. introductory matter, that can often help determine if the work is worth pursuing in the libraries.
Use DiscoverE to Browse shelves (you can also go to the stacks and physically browse!
Follow citation links or "related record" links if available in a search result from a database. See the Citation Tracking guide.
Target reviews as well as the original articles and monographs, esp. in article databases that give you the option to select reviews as a search option.
Unlock the "deep" structure of Database search interfaces. Checking for the standard features like controlled vocabulary, boolean operators, limiters and wildcard characters should help you familiarize yourself with a new database quickly.
Capture your results: Use bibliographic software like Zotero or Endnote to capture print or online book and journal citations or full-text articles and to automatically generate footnotes and reference lists. You can use Zotero also to annotate your readings or share your bibliographies online with other researchers. Another good popular option for PDF and citation management is Mendeley.