Describe questions (questions that ask of an argument’s “method of reasoning” or how the argument “proceeds”) have kind of a funny place on the LSAT. On the one hand, they’re not terribly common. You might see a couple on test day, or you might just as easily not see any at all. But the skill they test, describing reasoning with the subject matter abstracted out, is important to a lot of things on the LSAT.
Studying for the LSAT is a difficult and time-consuming pursuit. For one thing, it takes a long time to build familiarity with the way the test is set up. Furthermore, unlike most of the tests people have experienced their academic careers, the LSAT tests skills, not knowledge — so you can’t rote-memorize your way to a good LSAT score.