Please don't smoke in this room.
Please refrain from smoking in this room.
I don't mind if you smoke.
You are prohibited from smoking here.
You're prohibited from smoking here.
You must not smoke.
Please don't smoke cigarettes no matter what.
I don't mind your smoking.
If you will smoke, please go outside.
I long for a smoke.
Put out your cigarette. Smoking's not permitted here.
Please don't throw away cigarettes on this site.
Smoking does you harm.