This is arguably the most important factor when deciding which company to work with to improve your online business or your brand identity. Hiring a search engine marketing or recruiting company that uses only ethical search engine optimization techniques or "white hat" techniques will ensure that the potential risks of being dropped, removed, penalized, removed, or expelled from search engines are minimized. No one enjoys waking up to the unfortunate fact of "kicking Google" for breaking or bending the implicit rules of search engines or explicit terms of service.
SEO methodology / specific expertise
Can your expert SEO company optimize static websites built with only basic HTML? A premium Search Engine Optimization company will have experience working with websites in all popular programming languages and technologies, such as PHP, ASP, ASPX, HTML, Cold Fusion, Flash, etc.
Does your SEO company have experience optimizing static and dynamic websites? Can your SEO company optimize the use of different e-commerce packages and interfaces such as Monster Commerce, Yahoo Stores, OS Commerce, Storefront.net, and Volusion?
Depth optimization / intermittent services
The major SEO companies around don't actually do SEO at all – they're just submission services that either manually or automatically submit your site to different search engines or directories.
A segmented marketing company is a company that treats different parts of an optimization campaign as separate entities. For example, an optimization company may charge a premium fee only for "linking" or "content creation". This piecemeal approach could be harmful.
Successful optimization is the combination of multiple efforts on multiple fronts, sometimes simultaneous, sometimes sequential. Putting the different aspects of an optimization campaign together usually results in worse results than the overall strategy.