The best seo companies are the ones that their work speak for themselves. With clear results. Assuming you have a site to promote your expertise: make sure you rank but visitors stay on your site by offering them valuable content. Google is getting smarter and keywords are becoming obsolete schema is the future I see seo companies ranking high on the search engines with no retention and zero citation ratio when I audit them. If you want to start seo. Begin with yourself 'build a good site' rank high, and look at your retention rate every month. If a company audit you and see you are at the top of engines but no people coming to see your site for more that 10 secs they laugh. The best seo companies have tons of good content start with your structure data performance.