Keys to this operation include -
1. Making sure you have a bottle with an actual cork natch, and that it has been chilled. The cooling will decrease the internal pressure.
2. Finding the seam on the edge of the bottle neck and running the back edge of the blade (the dull side) directly along that seam (perpendicular to it) during your strike.
3. Hitting the glass lip squarely, but without a ton of force.
Move video and wine information at: http://vincollections.com