How to Crack a bullwhip with the Snake Killer
The crack demonstrated in this video is called the 'snake killer.' It's a nice crack for putting a fast succession of cracks close to the ground. Only the fall of the whip should be hitting the ground, which will happen after the whip cracks.
It can be fun to put a plastic water/soda bottle on the ground and try to hit it with the snake killer. When you can make the water bottle 'dance', then you know you've mastered this crack.
Also, when bringing the whip up, it's possible to bring it up to the side of yourself (the side opposite the whip hand) or straight up in line with the whip handle. You're less likely to hit your face if you bring it up to the side, however the whip is usually brought up straight when the snake killer is used in two-handed routines.