Scholarly Writing for Law Students: Seminar Papers, Law Review Notes, and Law Review Competition Papers by 
Academic Legal Writing: Law Review Articles, Student Notes, Seminar Papers, and Getting on Law Review by 
Look up the topics being discussed at conferences to get a feel for what sorts of issues are being talked about by academics, lawyers, judges, and other specialists in your subject.
Guides on specific areas of law may suggest starting points for formulating and researching a topic. Good starting points include:
An oft-recommended strategy for identifying potential note topics involves exploring areas where courts of appeals from different federal circuits have ruled dissimilarly on an issue of law. As noted by Prof. Eugene Volokh in Academic Legal Writing, although this approach can suggest a meaty topic, it also risks preemption should the Supreme Court take action on the issue. Before pursuing a circuit split topic, Volokh recommends making sure “the Court has denied certiorari or no petition has been filed and the time to file has run out” for all relevant cases (p. 37-38). He further advises talking to professors who specialize in the relevant area of law and in the Supreme Court to see if they think it is likely the court will review the issue.
Circuit splits can be identified via Westlaw or Lexis searches (e.g. "circuit /5 split"). The following resources for identifying circuit splits may also be useful.