Loren Baker at SearchEngineJournal has review for new SEO/SEMers on "9 Ways to Get Banned by Search Engines". The nine ways he mentions are as follows:
1. Cloaking
2. Spamming (Keyword Stuffing)
3. Hidden Text
4. Doorway Pages
5. Redirect Pages
6. Duplicate Content or Websites
7. Code-swapping
8. Linking to unrelated sites or bad neighborhoods
9. Link farms
Read the full and detailed explanations at SEJ.