Search engine optimization, commonly referred to as SEO is one of the most popular services offered online. SEO experts offer this service in attempts to make businesses compete favorably online. Most web owners do not have the knowledge and tools needed to make their SEO campaign successful. If you do not have the expertise or time needed to make your SEO campaign a success, you should consider hiring an agency that specializes in offering these services.
What it takes
Look at the nature of projects they have done before
Any expert you choose should have a proven record of 
accomplishment. As such, they should give you a list of sites they have worked on before and where they stand. The best indicator should be to look at their rankings in major search engines and other things like revenue generated. Therefore, if the references they provide you with do not feature on the first two pages, do not give that company a second thought.
Realistic offerings
An SEO expert does not have to assure you high rankings at super-fast turnarounds for them to be effective. If the deal sounds too good to be true, think twice. As a tip, you should use companies that offer realistic results and not those that offer guarantees. This is is quite important considering that the agency has no control over ranking algorithms. High rankings should be products of consistent efforts.
Experience
Like in any other field, experience in SEO matters a lot. You need to work with a company that has been tried and tested over time. Ideally, the amount of time the company has been in business is the best way to determine the experience that the organization is bringing to the table. When looking at the experience, you also need to look at the number and type of customers they have handled in the past. An SEO expert that has worked with many customers knows best what works and what does not.
White-hat practices
What strategies does the SEO expert use? This is a vital consideration to make during your search process. As such, you should ask them about the strategy they use and let them take your every aspect. The approach used should be simple and clear. In case you feel that there is something unethical about how they do business, it is high time you considered other alternatives. The idea is to have a justified SEO campaign that will not land you in trouble.