[moldyorangepeel]

If the air flows into your room then nobody outside will be able to smell it (exceptions apply for buildings where temperature is contolled by air).

If you are unfortunate enough to have the draft blow to the hallway, you might be able to change that. Find out which window has the strongest outward draft.

Once you have checked all of the windows to find out which window is currently having the strongest outward air current, use that window to smoke near. This has to be done in combination with making sure the air under your door is moving the right direction, or else your room may be unsuitable for stealth smoking.

I tape a piece of paper to the bottom of my door so that I can see the direction of the air flow in an instant.

Just remember that you should have the direction of the air moving into your room, and out the window. A fan in the window could be helpful in some places, but it won't eradicate the smell entirely.