When researching for your potential mentors make sure that they will be able to provide you the intellectual support that you so desire. It is also more important than you think they need to understand whether you feel comfortable with the style of mentoring and to see if you can easily adapt to the environment in his lab. Once you have identified your mentor, devote some time to understand your career goals and how your mentor can enable you. Although mundane it is important to understand whether you mentor has sufficient funding to sustain the five years of scholarship that you will be requiring. You may also want to understand if your mentor has access to professional networks and travel opportunities that might offer career assistance to you in the future.
As you begin to collaborate with your mentor clarify your goals and expectations. Work on your dissertation with the aim that the research work and expected timeline is realistic and mutually agreeable. Also, make sure to understand when you can schedule a one on one meeting with your mentor for guidance and clarification. Additionally, you would want to know the availability of your mentor outside the scheduled hours. Are they reachable by email or phone?
For a successful mentor-mentee relationship make sure to communicate with your mentor frequently. You would like to keep him about your research progress. Ask questions when you hit a rough spot. Your mentor can play a role in advising you based on their experience. So the process is meant to be collaborative by which you reach a solution. Even when your research progress is slow and you do not have much data to share maintain a healthy dialogue to ensure that you are not avoiding your mentor.
Share your academic and professional achievements with your mentor. Although your relationship with your mentor is friendly and cordial you would have to maintain a formal distance.