I'll be honest, every time I get prepared for any type of portrait, whether it's executive headshot or editorial, or maternity and newborn,  I think: "How would Annie Leibovitz light it?".
I try to copy her style, which she perfected over the course of a very long and successful career.  I don't really expect to ever achieve this goal, but I'll keep trying, cause in this pursuit I keep discovering little things which eventually will become the foundation of my own style.