There are several things that can be included in the SEO proposal depending upon the client requirements:
1) Status of the domain and the areas that can be improved upon
2) On page work including creation of SEO friendly URLs, coding changes, content optimization etc
3) Off page work that includes high quality link building through Web 2.0s, SBM, article postings, PPT/PDF/Video submissions etc.
4) Social media marketing keeping in tandem with SEO
These should be more or less included in the proposal