Those little moments of creativity

Alright, so you're writing now. You have a good plot and you only want to work on that one book. But there's a problem, you have more ideas. You know that if you start writing another book it will interfere with how hard you are trying to finish the first book, but you still have the idea. Solution: Keep an word document for ideas (or a journal). That way, when you're done with your book you can start another one. This is also a good thing to do because when you're having writer's block you have a pool of thoughts just waiting to be used. So fish for them.