Read previous sensory evaluation articles - Use Your Senses, The Basics, The Language of Wine, Wine & Bullfighting.
During my studies in Cal Poly's wine program, Sensory Evaluation was one of my favorite courses. To answer the usual first question: no, it's not because we got to drink wine during class. The most important thing I took away from this course was the ability to identify and verbalize what I was sensing. Finding the right words is the main struggle for less experienced tasters.