These techniques include:
- Keywords unrelated to site
- Redirects
- Keyword stuffing
- Mirror/duplicate content
- Tiny Text
- Doorway pages
- Link Farms
- Cloaking
- Keyword stacking
- Gibberish
- Hidden text
- Domain Spam
- Hidden links
- Mini/micro-sites
- Page Swapping (bait &switch)
- Typo spam and cyber squatting
Yahoo's Mayer echoed Thurow's warnings about spamming the engines. He explained that Yahoo! (and the other engines) take spam very seriously and spend a great deal of time and effort trying to eliminate spam techniques.
http://searchenginewatch.com/searchday/article.php/3483601