A couple months back, Google ran an I/O conference. What many people don't know is that Matt Cutts and the search quality team video recorded a session with site reviews and posted it for everyone to see. The video is over an hour long, but it is well worth listening to and in some parts, watching.
Here it is: I would suggest just hitting play and listening to it and flipping back to it when you need to see something:
This video can likely teach most people about SEO in an hour. For more advanced SEOs, Matt did make a comment about using the nofollow attribute for login pages. Watch the video at about 31 minutes and 40 seconds in and listen to it. Matt said:
The only time I use the nofollow on internal links, is maybe a login page.
Now, I doubt this is something Matt wants people to misunderstand, so maybe Matt will comment on this statement? ;-) Why is this statement a big deal? Well, recently, Matt said that the nofollow would waste PageRank flow if used, which got people thinking that blogs are doomed and got people to reconsider using the nofollow.
Forum discussion about that comment at WebmasterWorld.