Guidelines on estimating user stories in Agile

1. Understand the User Story:
Before estimating, ensure that the team has a clear understanding of the user story. The product owner or the person responsible for defining the user story should provide sufficient context and answer any questions from the team. The team should have a shared understanding of the user story's purpose, functionality, and expected outcomes.

2. Determine Estimation Scale:
Choose an estimation scale that suits your team's needs. The most common scales used in Agile are Fibonacci sequence (1, 2, 3, 5, 8, 13, 21, etc.), T-shirt sizes (XS, S, M, L, XL), or linear scale (1-10). Select a scale that allows for enough differentiation between estimations and avoids spending excessive time on fine-grained estimates.

3. Relative Sizing:
Agile estimation focuses on relative sizing, where the team compares the effort or complexity of one user story with another. This approach helps avoid the pitfalls of trying to estimate absolute time. Relative sizing allows for a more straightforward and faster estimation process.

4. Use Reference User Stories:
Create a set of reference user stories that the team collectively agrees on. These reference stories serve as benchmarks against which other user stories can be compared. The team can assign a standard estimation value to each reference story based on its complexity, effort, or size.

5. Conduct Estimation Sessions:
Organize estimation sessions with the entire team present. The team members responsible for implementing the user stories should be actively involved in the estimation process. Use techniques such as Planning Poker, where team members privately select estimation values, and then reveal them simultaneously, allowing for discussion and convergence.

6. Discuss and Resolve Differences:
Encourage open discussion during estimation sessions. If team members provide different estimations, have them share their reasoning and insights. This discussion helps to uncover assumptions, identify risks or dependencies, and clarify any misunderstandings. The goal is to reach a consensus estimation.

7. Update and Refine Estimations:
After the estimation session, update the user story estimates in the product backlog or Agile management tool. As the project progresses, continue to refine the estimates based on actual effort or complexity experienced during implementation. This continuous refinement improves the accuracy of future estimations.