Each sprint begins with a planning meeting. During the meeting, the product owner (the person requesting the work) and the development team agree upon exactly what work will be accomplished during the sprint. The development team has the final say when it comes to determining how much work can realistically be accomplished during the sprint, and the product owner has the final say on what criteria needs to be met for the work to be approved and accepted.
The duration of a sprint is determined by the scrum master or development team owner, the team's facilitator. Once the team reaches a consensus for how many days a sprint should last, all future sprints should be the same. Traditionally, a sprint lasts 30 days.
After a sprint begins, the product owner must step back and let the team do their work. During the sprint, the team holds daily stand up meeting to discuss progress and brainstorm solutions to challenges. The project owner may attend these meetings as an observer but is not allowed to participate unless it is to answer questions. The project owner may not make requests for changes during a sprint and only the scrum master has the power to interrupt or stop the sprint.
At the end of the sprint, the team presents its completed work to the project owner and the project owner uses the criteria established at the sprint planning meeting to either accept or reject the work.