My approach to headshots is different than most, I don't work on a package basis, as each of my clients have different needs and I prefer to speak with each one in person and discuss the type of shoot their looking for and a budget that works for both of us. I've found that the most important aspect of doing actor/model head shots is being able to develop a bit of rapport. If you don't feel comfortable with your photographer you'll never get the images you need to get work.
That in the end is what this is all about. Additionally if you don't have a clear picture of parts or jobs you're going after, it's difficult to get the kind of images that a casting director/art director will pick. Again this is the reason I spend time with each of my perspective clients before we decide to move forward. Making sure you get the images that "get you work", is the foundation of my business.