Well, if you want to read things by some of the top contributing users, a good place to start would be the "leaderboard" [1]. Click on one of the users names, and click "comments". These are usually pretty fun to read (especially from those with high "avg" karma).
Also, to answer a couple questions you will inevitably have while browsing through their comments or old posts:
1) There is a karma threshold for down-voting (currently 500).
2) The "expired link" page you see is a known issue and is unlikely to be fixed any time soon.
As for guidelines:
Always try to add to the discussion. Be nice. This isn't reddit (humor is fine, but stupid jokes are not). Upvote on quality of content, not appeal of content.
[1] http://news.ycombinator.com/leaders