At work last summer I had to train a new employee. The way I did it is I did the first little bit of the task and then I let her do the rest. I set one of the tables and then watched her set the next one. If at any time she messed up I told her what she did wrong and how she could fix it. If I could I would also say why we have to do it this way. This is the same method I used later when I had to train another employee. I showed them how let them do it tell them how and if I could why. I know I did a good job because my employer says I did a good job and that is why I get to train people.