I generally don't have much problems figuring out how much detail I want if only because I'm a very go-with-the-flow type of writer. This issue does rear it's head with locations, or buildings. They're so boring, no matter how visually cool they are . Heck, even when writing a rough draft, if an important building come up I'll write this:
[INSERT description of fancy building here later on]
I tend to write in the exact style I'd like to read everything, which means details on certain things that I would like to read that exact way, as well. For example, many seem to hate when a character is described within the first few pages of their introduction. As a reader, I love it when they are described because then there is a visual and I don't want to make up my own, since what often happens is that there's an extra little detail about their appearance dropped in 7 chapters later. Then I have to edit my visual of them. Since I prefer appearances to pop up soon as possible, so long as it fits with the flow of the writing and the story, I also write like that. Since i approach my writing like that, I have very little "too detail or not to detail?" dilemmas. I only gotta ask myself what I'd like, and if I'd find re-read value in what I've written!