Like every other product or service that you are considering investing your hard-earned cash in there are a number of things you should do before choosing a search engine optimization company to optimize your website.

1.Shop around and compare quotes
2.Find out in detail exactly what your SEO company is offering
3.Compare quotes again
4.Check out references and previous campaigns that the companies have conducted
5.Compare quotes again

However there are a number of things you should avoid'

Companies that stress the importance of Metatags
What little benefit the META keyword tag had a number of years ago is of less importance these days,

Companies that say they will submit your website to the major search engines
Search engines will find your site if you have a few links from other websites pointing to it. This "service" is very often listed to bulk up an offering and is pointless.

Companies that say they will submit your website to 40, 400, or 4,000 search engines
Same applies as above. But be especially aware of companies that attempt to fool you into thinking that search engines other than Google, Yahoo, and MSN could drive substantial traffic to your website. Sometimes these offerings sound fantastic, but any SEO company worth their weight in salt should (and do) know that this is a redundant activity that just sounds impressive to anyone who is very new to online marketing

Companies promoting "Black Hat" SEO techniques which could result in your website being penalized.
The following are only a few of the many techniques.

? The use of hidden text (hiding keywords by using the same font colour as the background colour).
Search Engines will see it and penalize you and your website

? Participation in "link farms".
This is a sure-fire way to develop lots of links to your website very quickly. It is also the fastest method for your website to be banned from all of the major search engines.

? Keyword Stuffing.
A practice where keywords you are hoping to compete on are stuffed into the ALT attributes of your images, the titles of your pages, and also within the body/content of webpages. The tip to follow is that if you read it out loud and it sounds weird' re-do it.

The following link will bring you to the Google Webmaster Guidelines

Spend a few minutes familiarizing yourself with these techniques and you will be in a better position to tell your SEO company that you want your campaign to be both professional and ethical.

A company "guaranteeing" your website will appear in the Top 10 results (my personal favourite).
Of course if you are willing to pay for an appearance in the Top 10 by using a company to handle a PPC campaign such as Google Adwords this is in fact possible. The problem is that once you stop paying, your site will disappear completely. If a SEO company guarantees that they can get you listed in the Top 10 of the organic results run a mile (or 1.4 kilometres depending in which country you're running). Nobody can make this guarantee because SEO companies don't know every algorithm (or their individual importance) for achieving top ten rankings.

When choosing a SEO company it is extremely important to know up-front that it is not a matter of having your home page optimized. Search engines don't rank an entire website. They index and rank each individual page on your site. By having every page on your website professionally optimized there will be a much greater chance of driving a large number of visitors to your site. Getting them there is half the battle. Getting them to buy is the other half. :-)