You have raised some important and interesting questions here. Let's start with the broader questions: How does one teach a three-year-old?

You may have heard that play is the work of the young child: This is absolutely true. Preschoolers learn best by interacting with their environment in a relaxed and inventive way. Your son will learn important concepts by building with blocks, playing in water and finger painting. It may not look as if your child is building skills for reading and math, but that is precisely what he is doing.

Let's take one small example to illustrate this point. In order to grow in reading and math skills, a child has to have a genuine understanding of cause and effect. To comprehend stories, a child must realize that one event triggers another in a predictable manner. To understand math concepts such as addition, your child must learn that the result or effect of adding numbers is a greater number. When your child leans one block against another and the first block falls down, he is on his way to learning cause and effect. This reasoning may seem terribly simple, but we tend to overestimate a young child's understanding of the world and how it works. Most children do not have a firm grasp of the concept that "if this happens, then that will happen" until age five! So you will want to give your three-year-old open-ended learning activities in which he is manipulating real objects

Another important point to remember when deciding how to teach your three-year-old is that young children learn best when interacting with others -- particularly adults. That makes watching television, filling in workbooks, listening to tapes or using a computer program less effective than playing a game or talking with you. We have been led to believe that computer software is "interactive" and can in some way act as another human being, but this is not the case. You would think, for instance, that a child could learn about cause and effect (or German) from using software. But so far, all of the research indicates that children need actual physical experiences and human interaction -- not virtual ones -- for proper brain development and academic success. (For more information on young children and computers, see "Failure to Connect: How Computers Affect Our Children's Minds for Better and Worse," by Jane M. Healy.)

Imagine yourself teaching your child German in the same way that you taught him to speak English. Begin by pointing out objects and naming them. You can do this while you and your child take a walk in the park, play with plastic animals or cook in the kitchen together. I know a high school Spanish who teaches students the Spanish words for clothing with Barbie doll gear. She knows that her students remember the word for "boots" if they physically touch them than if they learn the word from a language tape. Then, once your child begins to get single words, slowly build to two and three word phrases.

Certainly language tapes are useful for immersing your child in the sound of the German language. But if you can, learn the songs and repeat the phrases right along with your child. This will increase your son's enjoyment and will help to give context or greater meaning to what he hears. You can do the same with the picture dictionary. Point to objects and talk about them, ask him questions and show your enthusiasm for the words he is learning.

When you ask him to pick up his toys, or when you tuck him into bed at night, speak in German. Use lots of repetition. I suspect that he will be using these new words with surprising frequency.

I hope that you will find these experiences great fun for both of you. Guten Tag!