Product backlog refinement is the addition of estimates, detail, and the order of items that exist in a product backlog. This should be an ongoing process that offers the development team and the product owner an opportunity to collaborate on the existing product backlog details. During refinement, products are not only reviewed but also revised. Given all of this, it should not be surprising that it’s a best practice to refine your product backlog regularly.

Regular product refinement ensures that product backlog items are clearer and more detailed. Precise estimates are always based on increased details and clarity. With proper refinement, the development team can complete sprint tasks within the agreed timebox. A high level of transparency can be achieved by the manner in which the refinement is done – See more at: https://www.scrumalliance.org/community/articles/2016/august/why-you-should-refine-your-product-backlog-regular#sthash.0zuV0lpp.dpuf

Tips for successful backlog refinement
1. Schedule refinement meetings regularly. Two one-hour meetings every week are adequate. In these meetings, discuss size, design, order, strategy, risks, and optimal flow, among other aspects of product development.
2. Prioritize rigorously. The rigor helps to truly reinforce the notion of priority or order in your project backlogs. Choose one project at a time and ensure that you do not get overloaded. Factors that influence priority include customer value; business value, in terms of the generated revenue; technical value, such as solid solutions and reduced risks; and quality value. It is imperative that you look at the team and create a perfect balance among all these variables.
3. Examine your stories regularly. Some teams refine their stories only once. This, without a doubt, is a big mistake. You need to write them down. Reevaluate the wording, acceptance tests, estimates, and order. This can be important for both simple and complex products.
4. Use a timer. It is imperative that teams be aware of the speed at which the refinement is completed. For instance, they need to know how many items can be discussed within that short span of time. However, it is not necessary that all refinement stories be completed within the stipulated period. Regardless, ensure that clarity and proper understanding is achieved around the stories. Refining up to 12 stories per hour is quite reasonable.
5. Do not prioritize estimates. The ScrumMaster should intervene if the members of the team take longer debating the certain order of stories. There are instances in which you have to move on, even when an agreement has not been reached.
6. Spike more, talk less. In many refinement meetings, there is a tendency to explore every story at a deeper level. However, this should not always be the case. It can be much better if you research and write code and talk with real knowledge and learning. This can be more effective when you work in pairs or groups, looking at real codes and prototypes.

Conclusion
With product refinement, you are adding estimates, order, and detail to items in your product backlog. This should not be a one-off but a continuous process, wherein the product owner and the development team will collaborate on the product’s existing details. With regular backlog refinement, things become more detailed and clearer, and the development team can handle the product backlog within the stipulated time.

References
http://www.batimes.com/robert-galen/user-stories-ready-set-go.html

http://www.batimes.com/robert-galen/anchoring-your-product-backlogs.html

http://www.amazon.com/Scrum-Product-Ownership-Balancing-Inside/dp/0988502623/