Woody Allen has said that 90 percent of life is just showing up. For historians, I would say that 90 percent of doing good history is asking the right questions, coming up with the sources that let you answer them, and reading them well. But I sometimes think an important 10 percent is serendipity - going to the library shelves, for instance, and finding not the book you set out for, but one alongside it you did not know existed, which turns out to be much more important.