Here are some methods to get your site banned by Google:
- Keyword stuff your site by repeating keywords in the meta tags or in the text and of your website.
- Link exchange with a banned site or several banned sites
- Have you and several people report your site as Spam to Google
- Have a high keyword density for a particular keyword string
- Have several sites on the same IP address owned by the same entity with a high volume of link exchange. By putting all of your websites on the same IP address instead of spreading them around to several IP address - this will send a red flag to Google and get your site banned.