Outlining each course you take is a way of summarizing and synthesizing all of the material you have covered in a particular course.   Some people begin to outline their notes and the basic principles of the reading from the first week in the semester; others wait until it is close to the end of the course to try to pull all of the material from each course together into a cohesive outline. 

It is the process of outlining more than the end result that makes it worthwhile, as the process forces you to synthesize the material while you are organizing and reducing it into your outline.  It is during this process that many students suddenly understand the overarching themes of many of their courses, i.e. the policies and principles behind the case law or the development of a regulatory scheme. Although it can be very time-consuming, many students find it to be one of the most useful ways to understand the development of a particular area of law keeping in mind the points the professor finds significant. 

Moreover, the fact that it is time-consuming should not deter you from consolidating all of the material into some kind of outline; it is the process of putting your outline together that is the learning process.

Because it is the process more than the end result, commercially prepared outlines do not serve the same purpose as your own outlining of the course.  Commercially prepared outlines can be useful to some people at various times -- to consult when there is a question, or when the presentation of an area of law in the class was not clear; to consult as to organization when preparing your own outline; or to review in addition to reviewing your own notes or outline when reviewing the material in preparation for an exam.  However, to rely solely on commercially prepared outlines is not sufficient because you would be bypassing the important experience of processing the information and commercially prepared outlines may not cover the same material, or focus on the same elements as your professor.  Therefore, studying a commercially prepared outline cannot prepare you as well for your final exam as studying from your own notes and outlines.

For more information on preparing course outlines, see:

Carolyn J. Nygren, Starting Off Right in Law School 72-89 (1997)

Michael Hunter Schwartz, Expert Learning for Law Students (2005)

Ruta K. Stropus and Charlotte D. Taylor, Bridging the Gap Between College & Law School 41-51 (2001)

Dennis J. Tonsing, 1000 Days to the Bar--But the Practice of Law Begins Now (2003)