This time I link to our colleagues from Charlottesville for their excellent advice.
I have a couple of my own rules of thumb:
Be aware of the differential advantages of choosing someone who is quite junior (perhaps an assistant professor) vis a vis a more senior mentor who leads a large group.
The more junior mentor will have potentially much more time for the trainee, which is really extremely important for learning the basic skills of science, from experimental design through data analysis. However, because of their own usually untenured status, they may turn out to be extremely aggressive about first authorship. Thus there is potentially a situational competitiveness between trainee and mentor–a big negative.
The more senior mentor (aka a lab chief) will have much less time. She or he will tend to run the lab in a more delegated fashion and perhaps lab meetings will be the only opportunity for face-to-face contact with the boss. In these situations, the lucky trainee will often connect with some senior post-doc in the lab who will de facto fulfill the “hands on” role of the more junior mentor described above. The good thing about these situations is that a more senior lab chief often has a much more generous attitude towards authorships and even promoting the independence of the trainee. Remember, this type of mentor already has attained significant success in their career and so there is little or no incentive to compete with the trainee for credit.
One other characteristic of the more senior mentor: they probably have the ability to pick up the phone and secure the trainee a well-placed next job. This of course is very important.
Jim
Discoverers and Discoveries 