I think the Ivey guide is a good start, however I think its missing a lot of information(purposefully) to lead to pick up a coach. If you look on the web you can find a lot of programs offering admissions help. Your best bet is to call up a few programs and see exactly what their experience is: how long they've been providing admissions help, what their credentials are( did they work in an admissions department, did move from teaching the LSAT to providing admissions help).
I am without a doubt sure that Anne Ivey can provide reliable guidance help, but there is the cost factor, and with that she was the dean of U of C. If you are considering top tiered schools, look for someone with expeirence/knowledge of top tier schools. If not, find a coach who can provide you with the most information for what circumstances you are in. LoyolaUC and U of C will be looking at different factors SO...yes a coach is the right move if you considering it, but find the right one that fits you. A Porsche 911 is a great car and handles very well, but you maybe be better suited driving a Nissan Pathfinder if you live in CO--find a coach that meets your needs