Preparatory Work:

WARNING: This page is about a different car, the 2003 BMW X5, 2002 BMW X5, 2001 BMW X5, and 2000 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.

To avoid paintwork damage, tape off working area over large area at outlet of wire starter (2) with fabric adhesive tape (1)
Cut off required length (A) from cutting wire (A) = Window diagonal x 4
Check whether wire can get caught on rivets or retainers; if necessary, insert guide needles in bonding joint and guide cutting wire past

Fig 1: Cutting Off Required Length (A) From Cutting Wire
Courtesy of BMW OF NORTH AMERICA, INC.