The other person puts their hands face down hovering just above your hands. At this point, you should be facing each other.
Step3
Try to slap the top of the second person's hands by quickly bringing them up and over, before the other person can pull her hands away. If you manage to slap her hands, switch roles. Now she tries to slap the top of yours.
Step4
Keep playing back and forth, switching roles every time a person "wins." Keep score if you like, but it's just a fun, easy game to pass the time.