1. Check the condition of the windshield wipers; if they have cracks or other signs of damage, or if they scratch the glass, replace them. Regardless of their condition, replace the wipers annually.
2. To remove the wiper blade, move the wiper arm away from the glass until it snaps into place. Rotate the blade 90 degrees, press the latch and remove the blade from the arm.
(The original entry can be found on the portal BMWMan)