There are a few places you can start for recommendations. Ask other business owners you trust and work with. Ask vendors you discovered through a Google search – after all, you found them, didn't you? Check SEO groups and online forums like Search Engine Marketing Professional Organization, High Rankings and Search Engine Guide.

While you don't have to limit yourself to SEO firms in your area, it's almost a necessity to find an SEO firm that is comfortable working with small to medium businesses and has experience working in your niche.