"By pressing this join button, I agree that I am here to improve myself. I understand that my flawed reasoning will be pointed out. My feelings about that will be my own responsibility. I agree also that I will point out flawed reasoning when I see it, no matter whose it is."

I like the idea, but am not sure about the wording, you might want to check out the related concept of Crocker's rules

There are core areas of knowledge that seem to be part of the culture. For instance, AI and cryogenics. I have a sense that these things are common knowledge among LessWrong folks. New people aren't necessarily going to guess what these are. I've seen people being voted down for not knowing a topic well enough when it comes to these subjects that seem to be core interests of the group. The site encourages them to read the sequences, but that's a HUGE investment. Most people are not going to read everything relevant before joining. If newcomers had a limited list of short selections to help them get out of the "newbie" zone on the group's main topics, that would be beneficial to both the older members (who won't have to vote them down / hold their hand / wade through their comments) as well as the newbies (who will feel less confused).

Academian created a short list of the most important sequence posts here. I realize that it is fifty posts, not five to ten, which brings me to the next point I'd like the newb guide to address. While we don't require everybody to read the sequences, this is still a site that has a core corpus longer than the Lord of the Rings, has added much more content since then and often assumes at least a passing familiarity with several outside writers like Paul Grahram and Robin Hanson. Asking a question or two is one thing, but anyone who wants to get seriously involved needs to be willing to do a large amount of background reading. Flowing from that, the orientation might be a good place to introduce the concept of disagreement levels.