1. watch pre-existing shows and take note of what you like from those shows, but also what you DON'T like! that helps a lot with establishing a format that works for you and is also convenient for your appliers
2. small > big. less slots have more chances to be filled in, and it'll also be easier on you to write a smaller selection of ocs. less chances for people to be left out, people always learn the hard way that with a bigger cast most end up being side characters of a bigger plot surrounding a select few
3. be mindful with position slots if you're making them! you don't need the same amount of rappers as you need with vocalists, unless you have already a portrayal for the final group with a high number of rappers and rap lines in their discography
4. KEEP READERS ENGAGED! this is extremely important, survival show afs more than any other kind require an insane amount of activity on both sides. don't be afraid to reinforce it, and make sure you can update frequently enough to keep them active. in case you can't publish regularly, allowing things such as roleplay channels on discord or other similar things help. as long as everyone feels involved, the af can continue!
i think this is all i have at the moment. survival show afs are one pain in the ass if you don't have everything figured out but still lots of fun once you get into them! feel free to dm me any time if you need help for anything too :D