Coming from a long-time fanadventure maker (and general author + roleplayer), there's a lot of ground to cover beforehand! Now, this may not be the best advice, but it's all from my perspective, so.
1. Work at your own pace! Seriously. This stuff is exhaaausting. 2. Make sure you have your basic plot and characters down 100%, with no major changes to make! Lack of plot was how my adventure Dreambound died. 3. Also make sure you know where the story's gonna go. Have a goal in mind. 4. Be open to criticism! Luckily there's a thread for that. 5. Be sure to keep the mirror updated if you have one! It's a lot of work, but it pays off.