There has been a document floating around the web and some people think it is legit others feel it is not. Either way, if SEO or PPC is a part of your marketing strategy, it is a must read.
Here is what the document covers:
1) Understanding Search Queries: Why “broad searches” should give “broad results”. For example, if a user searches for “digital camera” and it returns Best Buy’s site, it should give the category page for digital cameras and not the product page for a Nikon D40.
2) Defining Query Types: Navigational, Informational, and Transactional.
3) Spam Labels: Not Spam, Maybe Spam, Spam. On the later two, the reviewer must include commentary as to why they feel the web page is Spam. The document lists the following as examples of Spam:
a) PPC Pages
b) Parked Domains
c) Thin Affiliate Sites
d) Hidden Text/Hidden Links
e) JavaScript Redirects
f) Keyword Stuffing
h) 100% Frame
i) Sneaky Redirects
Examples are given, which can be quite educational. Just hope none of your sites are listed in this document as Spam examples. 
4) How to Recognize Scrapped Content
If nothing else, it will raise your awareness in how Spam is seen online.
The main reason I started the SEO Revolution was out of frustration. Frustration at all of the lies and misconceptions that are posted in forums, given as advice in teleconferences, and even taught in live workshops. "So why didn't all of this work?" " Why wasn't my site successful?" " Why am I still stuck in a rut?" 