Miniature games are an excellent tool for chess lessons. They are short, so the student won't get bored, and they are usually exciting and packed with action! At the same time, they show general principles, and also show punishment for breaking those principles.
Here is a game I sometimes show to students, which demonstrates the dangers of leaving the f7 square weak. Many disasters happen to beginning players (and sometimes advanced players as well) on the f7 square, which is the weakest square in Black's camp at the start of the game.
This is a simple game which can be understood by even a beginner, if presented well. Here are some pointers:
* The Queen's Gambit (2.c4) can be explained by simply saying "White is trying to knock out Black's central pawn"
* Be sure to show what happens if Black tries to keep his pawn on c4, by playing 3...b5. This is a famous trap. When Black plays 3...b5, he creates a "pawn chain". White needs to attack the pawn chain from its base - so, 4.a4.
* On moves six and seven, have the student guess White's moves, which are good developing moves. Of course, their order could be reversed, and playing 6.Nf3 and 7.0-0 is acceptable as well. But be sure that they develop their knights to the c3 and f3 squares, which are definitely best here.
* Note that 7...Nbd7 blocks in Black's bishop. Try to get the student to guess the key move 8.Bxf7+, drawing the king out at the price of a bishop.
* The variations after the bishop sacrifice are very clear and easily explained. Let the student try to guess White's attacking moves.
If presented well, this miniature game is an excellent lesson for a beginning to intermediate student.