If the SEO firm you're considering has a guarantee, study that guarantee and all of the "fine print" carefully. If they're guaranteeing to increase the traffic to your site, that's fine. If they're guaranteeing an increase in your rankings, that's fine too.

But, if they're guaranteeing that you'll get a top 10 ranking, consider this guarantee carefully. There are so many factors that come into play when optimizing a Web site. For example, how established is the site, or is it brand new? How competitive is in the industry?

Does the guarantee require that you choose a three-word keyword phrase, under the assumption that it's impossible to get a two-word phrase ranked high, or even a single keyword? For one thing, that assumption is incorrect. Depending on the keyword phrase itself, you can certainly get two-word phrases ranked high, and even certain single keywords. So, if you go with that firm, you're going to have to choose keywords that are less popular than what you might have chosen otherwise.

Some firms require you to sign a form stating that there are no guarantees for top ten rankings, which keeps misunderstandings down from the onset of the working relationship. Here's what one SEO explains when customers ask him about a guarantee:

"I make an analogy about search engine placement in order to illustrate what it is like and why it cannot be guaranteed. Obtaining high rankings is comparable to predicting the weather. You can look at the clouds, you can check humidity, you can watch wind patterns, etc. These are absolutely necessary to do in order to have any idea about the weather, but you still can't say for sure that it will in fact rain. I can do page tweaking, submissions, link promotion, etc., and have fantastic results and be right on the money, or it can rain on me. Doing what I do is a necessity to have a decent chance at obtaining search positions, but I cannot promise how the rankings will perform."