Ooo Schedule is a good one. Once you figure out what length posts you like to write and style, you'll know better how much time it takes you to give partners a response. There's no better way to get burnt out, then to take on more than you can keep up with.
Setting up a good plotter/notes to keep yourself organized is good too. I like to have a link to all my threads with links to mine and my partner's character info so I can click around to find what I need easily while writing.
Really just have fun with it, I like to make my character first (like with DnD), whatever I'm in the mood to play at that time and just run with it. It's different in the sense that you and your partner(s) are essentially the DMs jointly, so be sure to contribute to the plot lines as much as your partners do.
Unless of course you're in a DM situation, then forget what I said lol