One cuts across all times. One concerns today's emerging needs. Professionalism is not a degree. It is an attitude. There are professional dishwashers and unprofessional lawyers.
Professionals stay to do the job right, no excuses.
To take that a little further, I also look for people who are curious about the library environment. Good librarians intuitively grasp that the library is a system, thriving on the vitality of all its parts. There are some specific mind sets that librarians will need over the next decade or so. Whether they are employed in libraries that serve schools, the public, the academic community, or special institutions, library workers need to grasp the power of the educational perspective. We build lifelong learners, we aid in formal education, we are conduits to essential professional knowledge.