A business plan is just as important for a service business as for a product-based enterprise; perhaps even more so. A carefully constructed image ("company identity") including promotional materials parallels development of an effective business plan. A personal selling strategy needs to be in place, including details of billing and contracting, before you begin, or at least get in too far. The chapter on "Planning Your Company's Finances" was of particular interest to me, since it is often taboo in casual conversation among colleagues.
I initially thought the author was extremely hard-sell, but to be successful long-term, confidence and forethought are essential. Competition is fierce in many fields, and you need to get and keep your slice of the target market pie. As I read further, reality set in, and this book is reality and experience-based.
Be honest, and go for win-win situations; you are in business to make money by providing honest, consistent, quality customer service. The last few chapters, particularly the chapter on ethics, provide nice segue to perhaps another book.
For the money, this is a good survival manual from the consultant's point of view for a beginner or a professional already in the field. It's an easy read meshing the marketing and business principles you'll need to supplement your given areas of expertise. For more complete (and pricey, but worth it if you're serious) information and advice, check out Elaine Beich "The Business of Consulting and Beyond" and/or Peter Block's "Flawless Consulting" sets of workbooks/case studies plus texts.
So Thomas L. Greenbaum is particularly helpful on the financial side of becoming a consultant. His book, THE CONSULTANT'S MANUAL, makes consulting dreams come true, along with Geoffrey M. Bellman's THE CONSULTANT'S CALLING, Herman Holtz's THE COMPLETE GUIDE TO CONSULTING CONTRACTS, Peter Meyer's GETTING STARTED IN COMPUTER CONSULTING, Janet Ruhl's THE COMPUTER CONSULTANT'S GUIDE, and Howard Shenson and Ted Nicholas' THE COMPLETE GUIDE TO CONSULTING SUCCESS.