What I do: I'm in college in student housing so I have to be EXTREMELY careful. Smoke in the bathroom and turn the fan on. Then turn the shower on as hot as it goes. This creates moisture which (supposedly) captures the smoke particles and neutralizes the smell. Put at least two towels under the door. Create a "boofer". This can be done with paper towel tube or a 20 oz bottle with small holes cut in the bottom. Stuff that shit with a lot of fabric softener sheets. Maybe even spray those down with Febreeze first. Exhale through the boofer to cover the scent. And burn incense. Nag Champa seems to be the best choice. Maybe it's just me, but that particular brand seems to cover the scent the best without being really nasty.