Google is known to change its algorithms many times per month. Google is also known to take drastic actions against spam, overtly suspicious activities and thin affiliate websites.
But although there are constant algorithmic changes, Google, it its guidelines is always telling us some things which never change:

  1. You should not spam ever!
  2. You should not get spammy links, because that will get you killed or penalized.
  3. If you link out to crappy websites, you will get penalized for sure.
  4. If you are dumb enough to use only 1 anchor text for thousands of links, you will get into trouble.
  5. We want you to give your visitors an excellent experience on your website.
  6. If visitors love you, we love you.
  7. If you are buying links, make sure we do not catch you. If we catch you, you will complain.
  8. If you do not have authority, you will almost certainly not rank high for the long-term.
  9. If for some reason you rank at the top for a keyword (provided you use legit ways to rank at the top), we will try our best to keep you there.
  10. The best links are those placed in-content (editorial links) and which come from trusted websites with high PR and traffic.