Now before I go any further I have to say that I fully support White Hat SEO techniques. But sometimes its worth knowing about the techniques that others implement in order to cheat the system.
Katrina, has been busy putting together a list of Naughty SEO tricks and bad practices and she discusses the pros and cons of using them.
As I've often mentioned in previous posts; Black Hat techniques do not pay off in the long run. The search engines are becoming wise to such techniques and anybody using such tricks could find their website being penalised from search results.
So check out what Katrina has to say, and make sure your website isn't implementing any Naughty SEO.