Original: Your article/note should offer original research, ideas, and/or conclusions; it should bring something new to the world of legal scholarship.
Topical: An article/note usually should concern itself with issues of current interest.
Unlikely to be Rendered Moot in the Near Future: It could be pointless to write on a circuit split if the Supreme Court has granted review and will render a decision before your note will be published. Also, avoid basing your article on volatile world situations that could change substantially at any time.
Narrow: You cannot take on the world. It is better chose a narrow topic and examine it thoroughly, than to be overwhelmed by a broader topic.
By Beatrice Tice, University of Michigan Law Library.
Blogs listed by topic
What the profs are discussing
State issues of concern
Tennessee issues of concern
Each of the books listed below has a chapter on choosing a topic: three varied approaches.