There's a great temptation to throw things in, as you put it, that you think are neat, or that you have a very clear, specific memory of and think you could do a good job writing about. What I find is that it's like a seed you plant. You can try it, and if it will grow and connect with other ideas in the book, and you can see connections that you can actually realize on the page, then you're allowed to leave it in. But if it just kind of lies there and doesn't really add up to anything or there's no chemistry with everything else going on in the book, then you have to take it out.