You can make a simple top by cutting a circular piece of cardboard, poking a hole through the center, and using a short dull pencil for the post. A short wooden dowel with a rounded end works even better than a pencil.
a. Try building such a top and testing it. How far up the pencil should the cardboard disk sit for best stability?
b. Observe what happens to the axis of rotation of the top as it slows down. What is the direction of the angular momentum vector, and how does it change?
c. What happens to the stability of your top if you tape two pennies near the edge on opposite sides of the cardboard disk?