Well, to start with, consider the guides already in existence. Unless you're attacking a diff. problem than the current guides, or can lay things out better than others, it's generally not a good idea to make a guide one something already approached. I'm not saying you shouldn't do it, though.
Be sure to make the guide easy to follow, keep a friendly tone throughout it and include piccies wherever possible. They help. Pros/Cons for picking a certain class, or a specific build is also good to mention.
Just keep in mind, it's a guide, it's meant to help the less fortunate ones, so it's best to take your time till you put it all together. Have fun and I'm looking forward to seeing your guide.
