1.2 Mark location of the mirror mount on the outside of the windshield
WARNING: This page is about a different car, the 2013 BMW X5 M, 2012 BMW X5 M, 2011 BMW X5 M, and 2010 BMW X5 M. However, it is still accessible from the selected car via links, so may be relevant.
Scratch off glue residue on glass and base with a sharp tool.