This one comes to us via our very good friend Raymond Ward at the (new) legal writer blog. The original post is from Concurring Opinions which does a great job compiling advice from various academics as well as providing sample cover letters. Among the advice is this:
Basics. Obviously, submissions must indicate author’s name and contact information (mailing address, phone, email) and article title. Unless submitted in an electronic format that transmits this information, the cover letter is the place.
Word Count. Many journals request stating the piece’s word count, including footnotes. In addition, many journals since 2005 have express word count limits or preferences, and request cover letter explanations for approaching or exceeding the guidance.
Brevity. Keep it short, usually a single page of three paragraphs, never more than two, and then only if justified by background research and context otherwise not evident from the piece.