A really cool professor is invited to give a seminar in my department, and I would like to ask him/apply for a postdoc position in his lab. I do not know, if he has any openings, but I do have a meeting/lunch scheduled with him, since my project is related to his research interests. I want to know the best way to handle this. Do I send a short email with my CV/cover letter before he arrives on campus or do I ask him in person? Thanks!
Conferences and seminars are not only here to present what you are doing, but also create and expand your network of contact with people from your field.
Any form of contact is good, provided you put the respect it deserves. If the person is too busy, maybe it's best to send an email or try to talk to him in a very short availability period and drop your card.
If you have a meeting, that's even better. You already got his attention, it's the perfect moment to ask him the question directly. If you're interested in his research topic, just ask if he's looking to having a post-doc on the subject. He might not have a position available, but maybe he can ask for one.
There is no official method to contact for a post-doc, unless it's advertised on a website, then the preferred method should already e described.