A messy backlog leads to a messy product.
1Detailed Appropriately
Don't waste time detailing a feature that is 6 months away. Items at the top are granular; items at the bottom are 'Epics'—big, fuzzy ideas that will be broken down later.
2The Refinement Ritual
Spend 5-10% of the team's capacity on refinement. This isn't just a meeting; it's an investment in future speed. It ensures Sprint Planning is short and productive.
3Ruthless Deletion
If a story has been at the bottom of the backlog for 6 months, delete it. If it's truly important, it will come back. A backlog of 500 items is just a 'Product Graveyard'.
