I recently came across a post titled getting things done like a Zen master. One of the techniques discussed is that of the to-do planner, a planner that integrates a to-do list with a calendar. It's exciting to me because it captures some of the motivations I had when building Planner for iPad. If something has a specific due date, it's a calendar event. If it's indeterminate, it's just a to-do. It's important to see both at all times.
The reason I suggest using a weekly to-do planner is because daily planners have too much room. Focus not on how many things you can get done in a day; instead, focus on one critical task that will actually have an impact on your life.