SEO expert needed to promote our website

We need an SEO expert to perform search engine optimization and link builiding for our website in order to increase overall search ranking with yahoo and google specifically. We only want ethical and professional method of SEO. For website content creation/update necessary for SEO, I need the provider to be able to assign someone from their team who is experienced and has expertise in copywriting skills. The content should utilize the keywords with the right densities/marketing of the site. We need a provider who can lead and advise us towards achieving our search engine ranking goal. Please be honest with what and what you cannot deliver based on our desired keywords and the current competition we have out there.