To teach children about something as complex as Albert Einstein's theory of relativity, it is important to get them interested in the subject using familiar analogies and concepts they can understand before moving on to more complex topics. A brief introduction to the life of Einstein and to previous theories he relied on is also helpful. Finally, having the children conduct demonstrations with familiar material is effective.
When dealing with the first theory of special relativity and movement, it is useful to ask children questions first, such as how do they know how fast they are moving when inside a car or a train. This can lead to a discussion of uniform motion, what Einstein meant by it and the physical theories he postulated in regard to it. The second postulate on the speed of light can introduce a subject to children they may have never thought about: that light moves at a certain speed.
Because the theory of general relativity is more abstract, it may be more difficult to explain it in concrete terms that children can understand. Creating imaginative games that touch on the concept of the slowing of time or the curving of space can help children better understand some of the ideas involved in this part of the theory.