The first thing you should look for in a SEO Firm is whether or not they use a non-disclosure agreement. Any SEO Firm who advertises who there clients are is putting their clients at risk to unethical practices that other SEO firms will use to get a website penalized or banned so they can help their own clients. Also, any SEO Firm that is producing results isn't going to want other SEO companies to be able to analyze their work so they can copy their techniques. Just like the Colonel won't give away their Original Recipe for their chicken no good SEO Firm would so willingly give away their recipe for results.
The second thing you should make sure you have is a good contract that guarantees results and all fees you pay should be based on results. Any company that isn't willing to put their money where there mouth is isn't worth taking a chance on. Also, read all the fine print VERY CAREFULLY! Some SEO firms will say they guarantee results but if you read the fine print you'll find that all they guarantee is that if you type your domain name in to a search engine that you'll be in the top 10. The only reason your site wouldn't come up in that case is if you were already banned. Being banned means that your site has been removed from the search engines data base for spamming or other unethical practices.
The third thing you should look for is an SEO Firm that encourages you to get information and rates from other SEO firms. If a company has a good service then they should be confident enough to not be worried about another company outdoing them.
The fourth thing you should look for is how willing they are willing to answer questions for you. I am always willing to explain exactly why someone's site isn't getting results and I will give them advice they can use themselves if they decide that they can't afford our services or if they're not ready to get started.
The fifth and most important thing you should look for is a company that wants to stick with you for the long run. SEO takes time to get results and it takes a lot of work to maintain those results. Even if you get to the number one slot for the best keyword in your industry if you decide that you're there and don't need to work on staying there anymore in about three months you'll start slipping and in six months you'll be gone. As more and more companies start using SEO to get results it's going to take more and more work to get results and keep them.
A good SEO Firm can do amazing things for your business. An unethical SEO firm can get you in big trouble that will take a lot of time and work to fix. Be careful when choosing an SEO firm and always go with your gut. If it feels wrong it probably is. If it sounds to good to be true it always is. I am always around if you have a question. I do work for an SEO company and as much as I'd like to get everyone who could benefit from SEO as a client I won't tell you not to go with a company besides the one I work for unless I am positive that it wouldn't be good for your business.
Next Week I'll go in to some of the more technical stuff about SEO.
Director of Marketing
VIP Search Engine Marketing