Ok, here's a fool proof plan that worked for me:
First off, you need one of these:
and one of these:
and finally, one of these:
Now, whenever you hear your parents getting ready to barge into your room because they think you're smoking, start up the smoke machine, turn on the disco light, and break out the blow up doll. If you have enough time, pull down your pants for the full effect. They'll never suspect you're smoking hookah in the house again.