With three years of grad school under my belt and three to go, I feel like I've accumulated a fair bit of experience that would make for good advice to people starting out. I'm going to start posting brief tidbits that have proven helpful to me. All of these will be tagged as "lessons from grad school".
Lesson 1: Listen to your advisor.
Your advisor is an experienced professional in your field and has gone through grad school before. Therefore, it is very likely that they have a pretty clear idea where you were, where you are, and where you need to be for the jobs you want. If they think a project is worthwhile, take the hint and spend time and effort on it. If they think a project is a waste of time, minimize the resources you devote to it. Their goal is to get you to the finish line of graduation, and they have a better idea of what is expected of you than you do. Just listen to your advisor.