There are a few key criteria utilized to evaluate search engine marketing vendors. The following are just a few of the most important: length of time in business, collective industry experience, number of employees, number of clients, size of clients, client and employee turnover, depth and breadth of service offering, pricing, proprietary services, industry credibility, client testimonials, success stories, strategic partners, philosophy and process. Look at their client’s visibility versus their own, as “search engine marketing” is a highly competitive term, and those that perform well probably have a little too much time and not enough client work to keep them busy. Be sure to ask for references if they don’t have testimonials and success stories.