SEO - Search Engine Optimization

Search engine optimization (SEO) is the process of analyzing your site and modifying it to enable search engines to read it, understand it and index (or catalog) it correctly. This is not rewriting the site or changing the look and feel. It is subtle changes, adding or modifying inconspicuous visible and invisible text so that the search engines can read the site. SEO is not 'spamming' the search engines - it is simply helping the search engines help you.
The need for SEO has become acute in the past few years. Web sites are being created with Java, Flash and images all of which search engines can not understand and ignore. If the content of your website is ignored by the search engines then they can't index your site, If your site isn't indexed then no one will find your site by searching for it in Google, Yahoo, MSN, etc. If no one can find your site then your hard work and money spent creating the site is in vain.
Search engines don't like this either, they want to provide the best possible results to visitors and if they can't index a website for any reason they may be missing great content that searchers are looking for. In fact SEO is so important, Google provides guidelines for choosing a SEO service.

SEO is an abbreviation for "search engine optimizer". Many SEOs provide useful services for website owners, from writing copy to giving advice on site architecture and helping to find relevant directories to which a site can be submitted. However, there are a few unethical SEOs who have given the industry a black eye through their overly aggressive marketing efforts and their attempts to unfairly manipulate search engine results.
Ask for explanations if something is unclear. If an SEO creates deceptive or misleading content on your behalf, such as doorway pages or "throwaway" domains, your site could be removed entirely from Google's index. Ultimately, you are responsible for the actions of any companies you hire, so it's best to be sure you know exactly how they intend to "help" you.
Avoid SEOs that talk about the power of "free-for-all" links, link popularity schemes, or submitting your site to thousands of search engines. These are typically useless exercises that do not affect your ranking in the results of the major search engines. At least, not in a way you would likely consider to be positive.
Most such proposals require users to install extra software, and very few users do so. Evaluate such proposals with extreme care and be skeptical about the self-reported number of users who have downloaded the required applications.
While Google never sells better ranking in our search results themselves, several other search engines combine pay-per-click or pay-for-inclusion results with their regular web search results. Some SEO's will promise to rank you highly in search engines, but place you in the advertising section of the engine rather than in search results. A few SEO's will even change their bid prices in real time to create the illusion that they "control" other search engines and can place themselves in the slot of their choice. This scam does not work with Google because our advertising is clearly labeled and separated from our search results, but be sure to ask any SEO you're considering which fees go toward permanent inclusion and which apply toward temporary advertising.
For your own safety, you should insist on a full and unconditional money-back guarantee. Don't be afraid to request a refund if you are unsatisfied for any reason, or if your SEO's actions causes your domain to be removed from a search engine's index. Make sure you have a contract in writing that includes pricing. The contract should also require the SEO to stay within the guidelines recommended by each search engine for site inclusion.
One common scam is the creation of "shadow" domains that funnel users to a site by using deceptive redirects. These shadow domains often will be owned by the SEO who claims to be working on a client's behalf. However, if the relationship sours, the SEO may point the domain to a different site, or even to a competitor's domain. If that happens, the client has paid to develop a competing site owned entirely by the SEO.
Another illicit practice is to place "doorway" pages loaded with keywords on the client's site somewhere. The SEO promises this will make the page more relevant for more queries. This is inherently false since individual pages are rarely relevant for a wide range of keywords. More insidious however, is that these doorway pages often contain hidden links to the SEO's other clients as well. Such doorway pages drain away the link popularity of a site and route it to the SEO and its other clients, which may include sites with unsavory or illegal content.

What are some other things to look out for?
There are a few warning signs you may be dealing with a rogue SEO. It's far from a comprehensive list, so if you have any doubts, you should trust your instincts. By all means, feel free to walk away if the SEO:

• owns shadow domains
• puts links to their other clients on doorway pages
• offers to sell keywords in the address bar
• doesn't distinguish between actual search results and ads that appear in search results
• guarantees ranking, but only on obscure, long keyword phrases you would
• get anyway
• operates with multiple aliases or falsified WHOIS info
• gets traffic from "fake" search engines, spyware, or scumware
• has had domains removed from Google's index or is not itself listed in Google

Source: www.google.com