Is it made of slate or glass/crystal? If it's slate, take a scratch pad and scratch it up a little. If it's glass or crystal, it'll take a little more elbow grease with rough sandpaper or a diamond pad. You've got to get the top surface roughed up by cutting into the surface. To make yelps, try making small ovals on the surface with the striker at about a 60-75 degree angle with the tip pointed toward you. The other thing you need to do is rough up the striker tip with some sandpaper so that it can get a grip on the surface.