Kevin, there is not a fix-it-all formula in the years ahead of you. I know you will try to look for one. In that process you will try to read about methodologies and the lives of physicists who were where you are right now. Indeed, nothing will account for the learning from your own future experiences. Here I am leaving you some words for you to take in your steps forward. First, the length scales in a PhD are going to be very different than in undergraduate. And second, you will have narrow much more your focus.