1) Get a compass (with two metal bits, not one metal bit and a pencil) and a piece of plastic (you can start with a CD case cover.)
2) Draw what you want your hologram to be at one edge of the plate (a simple shape, or letter) using ink or a marker or just gouge it with a pen.
3) Start at any point on the drawing, setting your compass to a fixed distance (1 or 2 inches) and use it to trace one light scratch on the plastic. The scratch should be as light as a non-damaging CD scratch, maybe lighter.
4) Work your way through your drawing, point by point, making scratches at the same distances. The more points you use, the better the hologram will look.
5) When you’re done, look at the field of scratches and tilt it in the light. Cool, huh? Now flip the CD case over and look at the other side.