The basic approach of all agile methods is to
- Define a goal
- Break the goal into incremental bits so that you can iterate towards the goal
- Periodically (at the end of each iteration) pause to evaluate both your progress towards the goal, and whether the goal makes sense.
If you have doubts about whether long-range planning in an agile environment is even possible, read Johanna Rothman's book Manage Your Project Portfolio: Increase Your Capacity and Finish More Projects, which I recently received a review copy of.
A project portfolio is "an organization of projects, by date, and by value, that the organization commits to or is planning to commit to." This sounds like a scaled up version of a product backlog that you might use to organize your work in an agile project, but with a longer time scale. So it's certainly aligned with agility.
In this book, Johanna motivates the importance of the project portfolio to enabling agile development, and also demonstrates how the technical and project management techniques of agile teams make it easier to define and iterate on a project portfolio.
Johanna is an expert on merging the human side and technical sides of projects. I learned quite a bit about managing people from Behind Closed Doors: Secrets of Great Management which she co-authored with Esther Derby. In Manage It!: Your Guide to Modern, Pragmatic Project Management Johanna discussed how to manage projects. And one of the more challenging part of managing a project portfolio is overcoming the resistance some people have to defining a goal for a project, a portfolio for a product line, and mission for an organization. In Manage Your Project Portfolio she shows how how to address common obstacles to defining a project portfolio, evolving it, and using it as a tool to allow everyone to understand where the organization is aiming.
And the benefits of a project portfolio don't just help with "fuzzy" concepts like vision, but can also help reduce and address items such as technical debt. In addition to an overview of concepts, and concrete guidance on how to address problems, the book interleaves stories that establish that this work is based on real-world experience, and help you to relate to the issues the book addresses.
I recommend this book to anyone who has a role in defining projects.