Add this to your list of priorities for graduate school: making a good impression on your professors. Why? As a graduate student you need to find someone on the faculty who will be willing to become your advisor or mentor. Moreover, jobs and academic fellowships often require references. Faculty are ideal sources of references. In addition, your professors’ perception of you could also influence your grades and ability to find a good advisor. Like it or not, perceptions matter.
Read the entire article,Making a Good Impression in My Graduate Department, 5 Rules