There's no way that I can write a full page on what you should and should not do in a Wiki. Simply keep in mind that this is a forum for creative thoughts and opinions, and that others have just as much right to their opinions as you do; don't start deleting things just because you don't agree with them. On the other hand, if someone leaves a comment like “wow u all suck", then it's perfectly legitimate to simply strike that comment from the page. For a much more detailed look at Wiki-style etiquette, visit
http://c2.com/cgi/wiki?WikiSocialNorms
Please note that this Wiki is slightly different in purpose than that one, so not all the ideas there are applicable here; however, it provides a good example of a Wiki that Works.
In terms of style, a good way to leave a new comment on a page is to put a medium-sized horizontal rule (say, with --) at the bottom and add your comments below it. If you wish, you may then sign your name at the end of your comment, like I'm doing here. --Cirne
And if you have something to say in response to another's comment, then simply make a paragraph break and add your response in italics. --Notcirne
And keep alternating like that for an entire thread of comments.
Go play in the Wiki Sandbox, or go back to the Wiki Introduction.