When I start getting close to the end of a novel, something registers in the back of my mind for the next novel, so that I usually don't write, or take notes. And I certainly don't begin. I just allow things to percolate for a while.
I never cease to be amazed why some of my friends became famous and others, just as talented, didn't. I've come to suspect it's a matter of wanting fame or not, and those who don't want it, don't get it.