Ideally, your position will be in a cohesive and pleasant department that will make it easy for you to concentrate on your science while participating in departmental goals. However, this is not always the case and, if schisms develop, you may be pressured to choose sides. Such a no-win situation can be a big problem for support at tenure time whether or not you tactfully avoid allying yourself with a particular party. Much has been written about the importance of mentors in ensuring a successful career path, especially for members of under-represented minority groups and women. You will need guides to the unfamiliar territory represented by your new position and institution.
Some institutions assign mentors because they want their young faculty to do well.
Even if you are in such an enlightened atmosphere, recruit other campus mentors so that you have access to a variety of advice. Take them to lunch. It is a compliment to them that you value their expertise, but be considerate of the other demands on their time. Recruit external mentors in your field of research and draw on their perspectives and experience. Get to know others on campus.