• In Team Explorer, select the team project for which you want to configure check-out settings.
• From the Team menu, click Team Project Settings, and then click Source Control.
• In the Source Control Settings dialog box, select the Check-out Settings tab.
• Select or clear the Enable multiple checkout box.
• Select or clear the Enable get latest on check-out box.
• Click OK.

http://social.msdn.microsoft.com/Forums/en-US/tfsversioncontrol/thread/a51fa7a8-d9ab-497b-a305-e5ef0c445ff2

http://msdn.microsoft.com/en-us/library/ms242869.aspx