Read your post and liked it. However, there is a thing or two that I would like to point out. Firstly, the client should realize that the results that they would get would totally depend upon their budget. A better budget would definitely enhance the chances of their keywords coming up higher in organic search results. Secondly, try to follow the blog of the SEO company and check if they update it regularly or not. If they do not have a blog then they are not professional. Also, check the testimonials and the websites of their clients.