The agile lead should evaluate the team's capacity and help them select user stories that align with around 80% of their available capacity for the iteration. This approach takes into account potential issues or interruptions and helps ensure the team is not overcommitting. By selecting user stories based on a realistic understanding of the team’s capacity, the team is more likely to meet their commitments and avoid incomplete work. This method promotes sustainable work practices and helps the team maintain a predictable velocity over time.