A Scrum Team works together against a common goal. There is a goal to release the product at a certain date, but there is also a goal for the current Sprint. The Team have identified a number of tasks in their Sprint Backlog that is needed to achieve the Sprint Goal.

Everybody in the team must together take responsibility to complete the tasks in the Sprint Backlog. In Scrum there is no (traditional) Project Manager who assigns tasks to the Team members. Each member must do this!

There must be a little bell ringing for the the rest of the team when someone reports that he is still working the the same task for three days. There must be a hidden impediment here! This lack of progress affects the whole team and jeopardize the possibility for the team to reach the Sprint Goal.

Everybody on the team must also have some basic idea of how the Sprint should be completed. Some tasks may have longer duration or are on the critical path and must be started early in the Sprint. When you pick the next task you have to have this in mind. Also watch out for people that pick fun and easy task that have low priority.