Make sure your sparkling wine is completely chilled (between 38-42°F). The internal pressure of a warm or room temperature bottle can cause it to explode in your hand.
Remove foil, wire cage, and metal cap.
Hold bottle by the base at approximately a 45 degree angle and aim away from yourself and others.
Find the seams of the bottle, and ensure one of them is facing up towards you.
Slide the saber along the seam up the neck of the bottle towards the cork and firmly (but not too hard) hit the lower lip near the opening of the bottle.
The neck will break in a clean line.