Depends really if your doing it solo do them as simple as you want, just make sure YOU understand it, don't even have to place dialogue if you don't want to, just make sure you have a rough idea where the
dialogue will be at the end
if your working with and edit or plan on asking other people to check your work make it almost rough sketch like and make sure the dialogue is in there
personally I'm doing the latter since I want my sister and other people to read it and give their opinions before I put ink on paper