You'd be amazed how well the shower works. Does your bathroom have a window? Because if it does, like mine, you can easily make a perfect smoking set up. ^.^

Just put a towel under the door, turn the shower on really hot, put a fan right up against the window to blow out the air in the bathroom and blow directly into the back of the fan. Your smoke will go straight out the window. Smoke for like 5 minutes, then take a 20 minute shower leaving the fan on. Close the window, and then leave the shower on really hot for like 3 minutes or so. Should steam up the room really well and your marijuana smoking tracks will be completely covered.

Now to avoid your parents knowing you're high...