When I embark on a new book I often have no clue as to what is involved in my hero and heroine's professions. So, I read a lot of books and watch films on the profession if they are available. But nothing is as profitable as interviewing an old timer who worked in the field I'm researching back in the day.
Pretty neat, right? I would say that meeting these people and doing these interviews is one of my favorite parts of this job.