I have to give credit where credit is due... I found this wonderful idea on the website below:
We have practiced drawing spheres in art (probably since kindergarten with Mrs. Wheeler!) for years. The students had to trace different sized circles, making sure that they overlapped, then they had to practice what they learned about drawing spheres and make the hook part of the ornament. They then had to draw the highlight. We discussed light sources and how the highlight should be on the same side for each (we don't want to get too complicated...).
We discussed painting them with watercolors and making sure to use analogous colors on each... colors that are next to each other on the color wheel. We also discussed how the highlight should be painted the lighter color. The results are fantastic. It's a holiday type of lesson and the students really seem to like it!