There are some Black Hat Methods of SEO Spam

Hidden Text

keyword Stuffing

Duplicate Content

Cloaking

Link Spammer

Redirecting

Black hat SEO is more frequently used by those who are looking for a quick financial return on their Web site, rather than a long-term investment on their Web site. Black hat SEO can possibly result in your Web site being banned from a search engine, however since the focus is usually on quick high return business models, most experts who use Black Hat SEO tactics consider being banned from search engines a somewhat irrelevant risk.

Doorway Pages
Hidden Text or Links
Keyword Stuffing
Cloaking
Article Spinning
Spam Comments
Duplicate Content