Danger Of Explosion!
WARNING: This page does not describe the selected car, but rather 16 other vehicles, including the 2006 BMW 325Ci, 2005 BMW 325xi, 2005 BMW 325i, 2005 BMW 325Ci, and 2004 BMW 325xi. However, it is still accessible from the selected car via links, so may be relevant.
After engine of vehicle to be started has started up, first disconnect the jump lead on the negative terminal/ground connection. Then remove jump lead from positive terminals. See 12 00... INSTRUCTIONS FOR DISCONNECTING AND CONNECTING BATTERY