Step 4: Improvements/Variations
Use sticky velcro tape and put one piece on the helmet and its mate on the flashlight. Then you can just stick it on and go.
Or you could just keep a few extra rubber bands around...
You can do the same thing to hold the light on the handlebar stem of your bike if you don't want it on your head. It is probably better for racing-type bikes because of the crappy position in which you have to hold your head to see where you are going.
I ride a recumbent so the top of the helmet is fine for me.