Planning & Estimation
Dwight Eisenhower gets credit for popularizing the quote, "Plans Are Worthless, But Planning Is Everything." Regardless of which project management approach you use, planning will be crucial to success. You will need a way to track requirements (user stories, product backlog items, backlogs, portfolios, programs, etc.), but you'll also need a method to estimate these tasks (story points, ideal days, cycle time, etc.). This information will be used to forecast roadmaps and release plans that convey your intentions to your stakeholders.