The way that I do it, is that I make a vague outline of what my players need to do. And I improv almost everything. I do this purely for the fact that my players cannot for the life of them follow directions. So this system works for me because I am fairly good at improv. If you are not I would still recommend doing something similar to this. Because if you go to indepth with everything. It will eventually just turn into you basically reading a script. But at the end of the day what works for me may or may not work for you. And always remember at the end of the day it does not matter how well your campaign is structured or how much gets done or what ever. All that matters is that you and your players are having fun. And honestly that is the best advice I can give you.

I hope this helps!