CosmicGamer:
If you have requirements, state them clearly.
This is the single most important detail for putting together RTJ information. Telling your players what you, as the GM,
need from them in order to work well with the way you're running your game is the first, best method of sorting out players.
Now, since GMs are all unique individuals, there is no single standard for what makes a good RTJ. You, as the GM, have to determine what you want people to have...what's important to you. Do you want people who have experience with the system/setting you're running? Do you want people who are highly literate and can articulate themselves well in writing? Do you want people who will post at a specific rate, come Hell or high water? Do you want people who are coming into the game without any preconceived notions of what it's going to be, so you can help them craft a group that will work well together? Do you want people who are really eager to play but maybe not necessarily proficient as writers?
You're the only one who can judge what takes precedence for you. The more stringent you are about your criteria, the less likely you are to have a lot of players apply. Those players, however (the ones who follow the RTJ requirements, at least) will come to the game with a clearer vision of what you intend to run, which (hypothetically) makes it more likely that they'll be on the same page as you when it comes to how the game runs.
I'd give specifics...but I can't, really. I've joined games where the GM presented you with a hypothetical situation and wanted a page-long writeup of how your character would deal with the situation. I've joined games where the GM specifically said 'no character concepts at this point, we'll put characters together as a group once I've selected players.' A lot of GMs are adamant about NOT wanting a writing sample. Some GMs insist on age statements, even though the game they are running isn't Adult (they just want to make sure they've got mature players, and even though age doesn't necessarily equate to maturity, your odds improve with older players).
So, very seriously, what to include all comes down to what you consider to be important and relevant.