First off, thanks for putting this together. It was very helpful for someone new to Gamers Plane.
A couple of things that I found that could have been clearer.
Big Issue #1: How to get to the game forum for a particular game. I had a devil of a time figuring out how to find the game forum. In my case, the first game I joined had a private forum, so I ended up just asking the GM. While this isn't really an issue with your guide so much as a usability issue with the site, I would have expected a link to the game forum from the game details page. I feel this would be especially important if the GM was using a public forum and placing the character creation information or a more detailed description of their campaign world, etc, in the game forum itself instead of the game description. For a new user, this was super confusing. Even as a user who has now been accepted into a game, the only way I know of to get to the game forum (besides the link from the emails sent by the forum subscription) is to go to the Forums Tab, have the Public Games toggle turned to off, and scroll down to my game's forum. From a usability standpoint, this sucks. The homepage has a link to the Game details, but not the forum. So, even once I'm in a game, if I don't use the link in the email, I'm having to take several steps to get to the forum where I'm doing the most important activity on the site (posting), assuming I don't just have it bookmarked:
1. Go to the homepage.
2. Go to the forums tab.
3. Scroll down to the Game Forums section.
4. Find the link to my game (If it's a private forum and I have public games toggled off, this isn't so bad. Otherwise, it's a pain.)
An improved version could look like this:
1. Go to the homepage. In addition to having the *games* I'm in listed with a link to the *game* there should be a link to the game forum.
2. Click on the link to the forum for my game.
Given the URLs involved, I wouldn't be surprised if all it took was a simple lookup of the forum associated with a given game, and building the URL for the link would be child's play (game ### -> forum ####, so a build a link to /forums/####). I'd be shocked if that information wasn't available in the database, and that relationship must already be modeled somehow.
Anyway, to get back to the point about the Guide, I'd explicitly mention that you won't be able to get to the forums from the game details page, in bold. Beat them over the head with this so they don't miss it, since it's something that I think most players would expect if they've been on a site like Myth Weavers or other PbP sites.
In Step 2: Find a Game, you have the instructions for applying under sub item 1. I think it would be clearer to have it separated into
a) finding a game you'd like to join
b) applying to the game.
When you first mention applying to a game, I think it would be helpful to restate that you'll be creating the actual character in the next step, after you've been accepted. I found myself wondering whether I should be worrying about character creation before applying. It felt strange to apply for a game by simply hitting a button, rather than posting to a forum and chatting with the GM about a character concepts, the campaign conceit, etc. If there's a particular accepted etiquette around chatting up a GM before simply hitting the button, an explanation of that might help reduce any confusion. In my experience on other PbP sites, getting into a game could be very difficult because there are so many players applying, and GMs often have to do a sort of audition process, where every applicant essentially pitches a character concept and creates a character sheet, and the GM sifts through them and then decides who gets into the game. Things appear to be different here, so maybe a quick note to any gamers who are coming in with experience from other PbP sites would be good, or maybe my experience here so far (hitting the apply button, getting accepted right away, then jumping into character creation) has been outside the norm.
I hope both of the suggestions are taken in the spirit they were offered. I love the look and feel of the site for the most part, and I was really impressed with the guide you put together. I definitely think new players could benefit from a better experience getting to (or knowing how to) get to the game forums, and getting a better intro up front to how the application/character submission process works.