A laser, no matter how powerful, is a beam of concentrated light projected from an emitter source. Although the laser is made up of light, it is typically only visible when it touches another object. Because the air normally doesn't have large enough particles to make the laser visible, you need to add some sort of material to the atmosphere to make the laser appear to be a continuous beam.
Things You'll Need
Power on the laser and point it at an object across the room. Set it down on a sturdy surface to prevent it from rolling away. If the laser does not stay on automatically, you may need to wrap tape around the power button to keep it on.
Coat two chalkboard erasers thoroughly with chalk. If you do not have chalk erasers, you can cover your hands with the chalk. White chalk is the best to use because it doesn't interfere with the laser's color.
Clap the erasers (or your hands) along the path of the laser. As the light from the laser strikes the chalk dust particles, the laser beam becomes visible.
Continue applying dust and clapping along the path of the laser to keep the laser beam visible.
Tips & Warnings
Avoid pointing the laser in the direction of anyone's face. If a laser comes into direct contact with the pupil, it can cause damage. Most laser pointers are not powerful enough to cause serious issues, but it is best not to take a chance where safety is concerned.