Map out a tentative research plan. Doing so will give you direction and will likely spark more deliberate thinking about where to search. More suggestions on how to formulate a research plan may be found in the RA Resources guide.
Use a research guide, those available on the NYU Library website and elsewhere online. Subject-based research guides have already pulled together key material on their topics. Consulting them can efficiently point you to the best sources. Oftentimes there will not be a research guide on the specific topic of your paper but there may be a research guide on the larger topic within which your paper falls. Use Law Scout to find research guides by topic from around the Web. Guides can also be found through general internet searches.
Ask for assistance early and often at the Reference Desk in the Main Reading Room. Librarians can suggest a strategy if you don't know where to start; advise you on hard-to-locate and hard-to-cite sources; confirm that you have exhausted all possible Library and publicly available resources; give you a pass to certain local libraries (required for most academic libraries), among other things. Note: You usually will not have check-out privileges at libraries if you are given such a pass.
Investigate content on more databases than just Westlaw, Lexis, and Bloomberg. While these are each deep and well-functioning legal databases, it goes without saying that many topics will need material from and citations to materials not available on those databases including monographs, articles, data, interdisciplinary articles, historical sources, and so on. Also, simply stepping out of the Westlaw, Lexis and Bloomberg Law box may spark crucial new ideas and directions.
Sign up for current awareness services related to your topic. Current awareness services come in many forms--legal newsletters, new publication alerts, search alerts and so on. Alerts can potentially have a big long term payoff for the minimal work of setting up an alert initially. They can give you new ideas and keep you informed of developments as you write your paper. Understanding current developments in the area can also deepen your understanding of the subject area and enrich your insights for your paper.
Keep notes of where you’ve looked & search strings you used. Do this during preemption checks and during the main research stage. This will help you avoid having to duplicate your work unnecessarily. Further, when you are first starting a project, it is easy to not recognize the relevance of something you found that may be helpful upon later realization, given that one might not completely appreciate all the intricacies of the subject matter at that stage. Thus, if you don't maintain notes on your research trajectory, you may have difficulty retracing your steps where needed.
Try the Internet Archive to try to locate content that is no longer online.
Update your research. For primary materials, the major legal databases will contain tools to check for currency and validity. These include Westlaw's KeyCite and Lexis's Shepardize. For secondary materials, setting up alerts from current awareness sources on your topic may be helpful.
When are you finished your research? It is often said that when your searches keep yielding the same results you are finished. Another way to think about it: Are you getting so many repeat results that you believe that the chance that there is significant material out there that you haven't found is pretty small? Have you located the full range of primary authorities and authoritative secondary sources for your topic? Also, time permitting you might also continue to search during the writing stage. As your understanding of a topic develops so will your ability to find relevant material. You will gain a better sense of where to search and how to select keywords.