Finding a topic that is appropriate for a law review article (or a seminar paper) is challenging. The topic needs to be substantial enough to merit 20 or 30 pages of discussion—and yet small enough that you can say something meaningful about it. It needs to be current and interesting enough for editors and readers to want to read it—but not so hot that dozens of journals already have comments ready to go. The topic (or your take on it) should be novel—and yet you want there to be some material published about it so you have something to work with.
Above all, you need a topic that you find interesting and care about enough to work hard on for weeks and months.
Below are a section listing others' advice and then sections with search techniques and tools you can use to help you find and develop topics:
See the sources in General: Texts & Advice. Almost all of the books and articles about scholarly writing discuss topic selection.
In addition, see:
Ruthann Robson, Law Students as Legal Scholars: An Essay/Review of Scholarly Writing for Law Students and Academic Legal Writing, 7 N.Y. City L. Rev. 195 (2004). HeinOnline | LexisNexis | Westlaw. Compares and criticizes books by Fajans & Falk and by Volokh. Emphasizes that the student writer's passion for his or her subject is of primary importance in topic selection.
LexisNexis, Researching for Law Review or Journal (2012). Short (4 page) guide discussing topic selection and preemption checking.
Heather Meeker, Stalking the Golden Topic: A Guide to Locating and Selecting Topics for Legal Research Papers, 1996 Utah L. Rev. 917. HeinOnline | LexisNexis | Westlaw.
Includes tips on how to find a topic, different types of topics (traditional and nontraditional), and how to conduct preemption research to determine if the topic you are interested in is the topic of an existing article.
Westlaw, Guide to Law Review Research (2009). A 33-page guide to selecting a topic, conducting a preemption search, developing a topic, checking citations, and related subjects.