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.
Knowing the vocabulary is a first step. Using a tool like the Aroma Wheel is also helpful. This visual tool moves from broad categories in the middle to more refined descriptors on the outside. The vocabulary used to describe wine aromas and flavors can be daunting to say the least as it seems to be ever-expanding as people try to make things more complicated or 'sophisticated'.
Aroma sample lineups are useful to connect descriptors to perception. These are prepared using fresh ingredients and/or aroma essences: prepare each aroma sample in a separate wine glass, label, and organize by category on the tasting bench (fruit with fruit, etc.; the more is not always better as your senses my get confused or tired). This allows taster to become accustomed to a certain aroma on its own before applying them to the wines on hand at a tasting. For example, a Sauvignon Blanc wine tasting can have aroma samples such as bell pepper, fresh grass, lime, and passion fruit.
Having other people's opinions is always helpful. They don't have to be wine experts, just a group of friends that all have a common love of wine. I can't remember how many times I've been evaluating wines and didn't even notice a certain aspect until someone else mentioned it!
Tasters will often 'disagree' on descriptors when referring to the same aroma/flavor. For example, you might say there is a peach flavor, while I call it apricot. Bear in mind not everyone will use the same word choice, and there will be connotative and colloquial differences. Don't get frustrated or discouraged if you taste a wine and your descriptors aren't identical to, say, the winemaker's notes or a critic's review. It's a personal adventure and not always about what others think.