Self-promotion is the most difficult part of being a freelance photographer for me and for many other freelance photographers I know. If you are not careful to guard against it, your work becomes a part of who you are, your essence--your soul, which in an artistic sense is not always a bad thing. But in the commercial world of freelance photography we all know how hard it is to lay that part of yourself open to the dreaded REJECTION. I'm still struggling with that issue.
In an earlier post I mentioned John Kaplan's book on portfolios; now here is a book I found helpful along the same vein called "Successful Self-Promotion for Photographers" by Elyse Weissberg. It deals with putting together a portfolio but is a little heavier on marketing. John's book touches on marketing but is much heavier on the portfolio side of it. The two books complement each other very well.