I'll be starting graduate school soon, and when I look back at my college career, there are certain things I wish I could have done differently. In hindsight, I wished I wasn't in such a rush to study [insert your favorite hot topic here] as opposed to pinning down the fundamentals of the course materials I was studying. Probably the best class I took was a seminar where the prof had us read and discuss from classic texts in differential geometry and pdes. Anyways, now that I'm starting graduate school, I'd like to avoid other common pitfalls that graduate students make. So my question is:
What are common pitfalls, mistakes or misconceptions that you wished somebody had told you were wrong? I'm interested in pretty much anything from how to conduct research, to what courses to take, or anything else.