Life used to be simpler. In the early 2000s, if you wanted to go "agile," XP was the route of choice. And then Scrum became popular. And it was not too long before organizations began to hit the limits of these approaches due to their focus on teams. And then it became apparent that lean principles could be applied to software and Lean Software Development and later Kanban were added to the mix. Now, you have a great many choices: Not just about which method to use, but where to start, whether to go top-down or bottom-up, and what should be the scope of your effort.