In this tutorial i will give you some tips on Adventure map making!
(this is my first post so post in the comments if i did anything wrong!)

1.Plan out your story first OR either if it is a CO-OP or challenge map, make sure your plan all of them out. Having a map without sequence will make it nearly as useless and messed up

2.Set up the world perfect for your map(challenge maps people might want super flat world) as if you want natural generated ponds use default but if your map is big and you don't want to clear hills and trees and all that use super flat world

3.ALWAYS get more builders or helpers. More people means the work is going to get  faster and easier(always have friends to help you)this will make your map more interesting and if you have proffesional builders, your job is quickly done and also will look fantastic. Nobody will play your map if there's at least bad or poorly made buildings

4.If your doing hardcore redstone contraptions, always research how to do it before testing it as it might go wrong :) (once my failed contraption always teleported me and my friends in one whole loop when we on our own creative server which is hosted on mines)also don't do redstone near water, if the redstone updates the water your creation will be completely destroyed

5.Lastly, Always make large and outstanding buildings to make your map more interesting and more fun.if you have more people playing the map always update it for them!

I hope these tips can help you out on your adventure map!

Bye!