i don't really think you need to do one of these since deviant art already offers a how to of everything to do with deviant art

First-off, It's just dA, not "the" dA... and there's some grammatical problems but they're pretty minor. I'll tell you those if you want me to, but for the most part I'd say that's a lesser point of concern.

For thumbs I'd suggest putting in the whole code :thumbdeviation#: in there, so it's clearer what the end result should look like. I'd say do the same for deviant icons and links, but those show up as actual links and icons in my post, so maybe show them with quotations, like :dev"username": and :icon"username":, just so it's easier to understand.

You mention DD's, newest and popular as the kinds of images on the front page; don't forget prints as well. In fact you should have a section about prints in general, explaining what a prints account is and the basics of how it works, as well as how people can submit a print.

Be careful, under Getting More Involved you say "no-one's going to stalk you" but the sad truth is that it happens far more frequently than it ought to. I could just see someone reading this guide, winding up having a bad experience of that sort, and then making sure you never hear the end of how you told them it wouldn't happen. Probably better just to leave that line out and stick to positive reinforcement. On that note also, probably better not to use the word "idiotic" in "so don't say anything idiotic"... "don't say anything you'll regret" would be better.

The "Such and such will lead to Death" lines are major overkill. Having a set of basic rules is a good idea, but Keep It Simple, so the dense ones will understand what you're trying to say.

That's all for what I found, good luck getting it finished!

I gave a look at it and find it rather confusing. You start explaining how to make links (and actually it's be less confusing if you'd show the full code :devusername: and :iconusername: ), then you talk about deviations without explaining how to submit your artwork (or at least linking the FAQ #79: How do I submit Artwork? / FAQ #615: How do I submit a Flash animation to deviantART? / FAQ #286: How do I submit Literature? ), then you talk about how to get know, and end up saying that people leaving the site should allow other people use their usernames (which in my opinion isn't always a good idea especially for people that have been around for quite some time).
Anyway I think you should try to find an order for these information... Maybe explaining what is deviantART and how it works, then you talk about deviations, then how to make comments (and links), and so on...
but that's just my opinion