There is a great post on Lifehack about learning. We find in the post a quote attributed to psychologist William Glasser to keep in mind when we prepare a training:

We Learn…
10%…of What We Read
20%…of What We Hear
30%…of What We See
50%…of What We See and Hear
70%…of What We Discuss With Others
80%…of What We Experience Personally
95%…of What We Teach Others
–William Glasser

I already see that quote attending a “Train the Trainer course” but I still find it amazing. As a summary we can say that we learn better when we are involved.