SEO is something you'll want to not only read about but learn and get good at by DOING - once you start to gather good information [check through some of the threads here on VAF in this section and visit SEOMoz too as a good first start] use your own site or a sample site to test out what you're learning.
Because the search engines, Google in particular, will change their algorithms and you can never really know what those are, you'll find the right 'formulas for success' through trial and error.
One bit of advice, when you do start to offer
SEO as a service - be sure your own site is fully and properly optimized.