Pitfalls and No nos. Be very cautious of organizations that promise very high listings for almost nothing.
Search Engine Optimization is not something that comes easily. It takes quite a bit of work. People who promise high listings for almost nothing, don't fall for it. People who offer results in engines that do not allow paid inclusion. Its funny when a search engine optimization company, like ourselves, is pitched an obvious scam. Such as "we can get you the top listing in Google". Please be wary of such scams. It's funny, I have even heard of Google getting spam to the effect of "you are not listed in some search engines, act now!"
There are also techniques that you may come across that try to take advantage of some kind of exploit on the various engines. They do not pay off in the long run. If you happen to be into quick profit, quick scam, etc. be my guest. But in the long run you may get burned. It is well known that Google, the biggest and badest search engine, maintains a penalty list - not the place you want your web site to end up. Just stay away from any games and tricks. Develop a good clean, content rich site, and you will prosper.
Link farms, or sites that are primarily links, are something that you should stay away from as well. If your site is nothing but a vast array of links, I hope that you know what you are doing. There are several sites on the internet that are just link farms, and are successful, but the developers have to take care not to create a situation that engines find unfavorble. Additionally, if you are seeking links from other sites, try and stay away from abusive link farms. Take a good look at the page that you will be listed on, is it a quality page? Would I want people that find this page, to also find my site? How many other links are on this page? Is the listing or links page paginated and what page would I end up on? In other words, would the link to my page end up on page 23 or Just take a good look at all sites before you solicit a link from them.