It's easy to get caught up in the big picture of your novel and forget your character is wearing a watch for no reason. I was so zoned in on figuring out things like power and back story, I didn't realize that although I had gotten rid of most indoor plumbing in my village, a character's house still had a bathroom, again, for no reason.
If I'm not writing my stories, I'm thinking about them. Often, my mulling reveals a detail I overlooked. The novel I'm working on now has been in progress for years. This is like the umpteenth time I've edited it but I never picked up on these things. It's funny how I'm noticing them now. Remember, the more you write the better you write.
I also need to draw out what my village looked like when it was first created and what the world was like back then. What I have in mind doesn't coincide with the "present day" village. I either need an explanation of the gap or change something. Since history is coming out more in my new draft, I need to pin down how long the village has been there. Because of the back story, my village is turning out to be a lot younger than I thought.
For the most part, my characters live in the middle of the forest so, I need to figure out what their buildings are made of, what they look like and how they are maintained. I've been so focused on the houses of my main characters, the rest of the village was just neglected.
These details may seem insignificant but, more then likely, someone will read my novel and be seriously turned off by my world because these little details weren't fleshed out. If there is even a crack in my story, I need to fill it.