Automatic Case Assigning to team members

Business Scenario :

                             whenever any case is created in Dynamics CRM and when it is assigned to a team, that case should automatically get assigned to the first team member of that team. Once the case is assigned to the first team member, and if a new case gets assigned to same team again then that new case should be assigned to the second team member instead of first one.

Can some one tell me how can i achieve the above Scenario step by step i am new to MS CRM