Some of my courses make use of wikis. The one I usually go with is PBworks. If a wiki is used in a course, you will receive an invitation to join the wiki at the beginning of the course, when I enter the email addresses of all students in the class (for this, I will be using your official email address on file with the university - it is your responsibility to keep that updated. Not receiving the initial email is no excuse for not being part of the wiki). When you receive the email, you may have to get a subscription to the wiki (basically, that just means setting a login and password). That will allow you to participate.
Once you have logged in, you will be listed as either a reader or a writer. If you are a reader, that means that you have access to all the content on the wiki, but cannot change anything. If you are a writer, you can both read and edit the page, including create new pages. Most students in a course will be listed as writers. All new creations and changes are listed under "page history", so if there is any question about how a page got to be the way it is, everyone can always tell. Only the administrator (usually me) can change the page history.
You may also notice that each page comes with a blog-like feature that allows you to make a comment below the page itself. This will often be useful to discuss potential changes on a page before they are actually made.
So, how do you create a page? Look in the top right corner - you should see a link that says "create a page". Just click it.
You'll get several options for the kind of page you want to create. The page needs a name; make sure to give it one. Generally you'll just want to use the "blank" template. Once you've done those things, click "create page" and the page will come up.
It will come up by default in "edit" mode. You can see a couple of little tabs toward the top of the page on the left, under the title. "Edit" should be selected. You can type in content, or cut and paste (note: in order to paste, you might need to use the "Control-V" command). You can also format your work using the built-in editor (e.g., define headings, bold, italic, center, etc.) Once you have what you want (or before, if you want to be safe), you should click the "save" button toward the bottom of the page. That will save the document to the PBworks server, and automatically send you back to the "View" menu. Don't forget, if you want to edit some more, just click the "Edit" tab at the top, and you'll be back in the edit window.
For most classes, I will set up a sidebar for each wiki, which will serve as a table of contents (there may be exceptions to this - if so, this will be discussed in class).
You can, however, fill in a link yourself while in edit mode. If you highlight some text and click the "link" symbol in the toolbar at the top of the edit window, you will get several options for linking. The first one is always linking to another page within the wiki itself, and you can do that by just selecting that page from the sidebar on the right, or from the "recent documents" window). You can also link to an external document (something you may need to do for annotated bibliographies in particular); that is usually about the third option.
If you get confused, the help files (accessible whenever you're in "view" mode - the link is on the right at the top) are quite good, and should be able to answer most questions.
One note about the limits of the wiki: the free version of this wiki, which is what we are using, has a limit of 10 mb of upload space. That does not include the wiki pages itself, but rather documents such as pdfs, word files, or powerpoints which are uploaded to the PBworks server. Obviously, that's not very much space, and so I ask everyone to not upload documents unless necessary. If you want to link to a powerpoint you made, upload it to some other web space that you have, and then link to it from the wiki. The preferred mode of working with the wiki is to create a page and insert text into the new page.
The real strengths of the wiki format are collaborative learning and working. It is my hope that, as presentations are put on the wiki, and as prospecti and annotated bibliographies are put there, you will look through what others are doing and improve your own work, and also suggest improvements to theirs. Maybe you know of a good source that someone else should know about - put it up, or put it in a comment for them.