The GRE is an adult version of the SAT exam, with both verbal and quantitative sections, as well as analytical skills testing. It would be smart for you to prepare instead of taking your chances cold turkey. It's not that difficult an exam, but that interpretation is different for different people. If there is a practice exam available at your school (through Kaplan, etc.), sit for the test to assess the areas where you need to improve. It's probably not necessary for you to sit through a test prep course, as many of the test prep people (e.g., Kaplan, Princeton, etc.) also put out books with the same materials. Unless you need guided instruction throughout your study process, I'd suggest grabbing a prep book, setting goals for yourself (in terms of areas for improvement, score aims, etc.), and putting yourself on a study schedule to achieve those goals.