Let me start out by saying 90% of the SEO companies are out to scam you, so be careful. Here are some tip-offs that the company who is pitching you should be avoided:

1. They talk a lot about “meta-tags.” Sure, the description meta-tag is still important, as it’s used as a short description on the results page. Modern search engines are looking for good, relevant page content and link authority, NOT hidden content.

2. Reciprocal link exchanging is a central aspect of their strategy. Search engines, especially Google, consider excessive link exchanging to be a violation of their guidelines and will penalize you for it.

3. Submit to 300 search engines! There are only 3 or 4 that really matter, and it doesn’t take much time to submit to them. Submitting to the other 296 certainly won’t hurt, but it isn’t the key to making your website a success.

Things you should do:

1. Ask for references. Actually contact them and find out how successful their client relationships have been. Make sure improvement has been long-term. The danger of looking only at short-term success is that an unethical (black hat) SEO can get you huge short-term improvement, but get you banned in the long-term, long after they have your money in their bank!

2. Ask for guarantees. You are generally going to be paying a lot of money for and SEO service, so they should give you some kind of guaranteed position, or improvement in position.