Windshield wiper maintenance isn't something you want to save for a rainy day. Besides posing a hazard in bad weather, old and worn-out wiper blades with cracks or tears can scratch your windshield, necessitating a costly repair bill. You should take your wiper blades to an auto parts store and refer to the reference catalogues -- usually next to the wiper blades -- to be sure you get the right part for your particular Audi model.
Pull the wiper arm gently away from the windshield until it locks into a perpendicular position.
Swing the windshield blade back from the arm so that it faces you.
Press on the release tab. It's generally on the arm where the blade meets the arm.
Pull the blade out slowly. Slide the new blade into the arm until the release tab clicks.
Test the new blade by pulling gently on it. Return the windshield wiper arm to its original position.
Repeat the process for the second blade. Pour some water on your windshield and test the new blades.