Last Saturday, I accidentally made a powerful over head smash. I was excited, trying to repeat that throughout the game.
I went home to do some research on the internet. There were some nice youtube videos showing proper smashing technique. I guess I found out the trick. It is to tilt the body sideway, and raise the elbow, position the elbow behind the head, point the racket head downwards behind the head, swing the racket from right to left. The idea is to swing the racket head the longest trajectory before hitting the shuttle. At the point where the shuttle is hit, the racket should have gained enough speed and power to generate an explosive smash.
Simeon commented my smashes today are 30% more powerful. That is really exciting. I need to refine the smashing further, to execute it naturally every time. My right arm is aching at a different position after the intensive games today.