Ask your search engine optimization service for references. Due to the nature of the service, it may seem difficult to tell how well the service is performing for you, so it is necessary to contact companies which have previously worked with them.
Choose a search engine optimization service which is familiar with your industry.
It is important to have regular, on-going contact with your search engine optimization service during the duration of the relationship.
Have the search engine optimization company provide you with an outline for their services. Know what they intend to do and how they will achieve your desired results.
Understand it takes time to see results. Be wary of any service saying they can get you great results quickly.