I can tell you what doesnt work, bugging them everyday about how they should quit.  In my experience, people just get annoyed everytime someone tells them they should quit and why.  As with any addiction, the first step is them admitting they want help.  I had a CW who smoked like crazy then one day told us she was quitting.

Now, once the person says they are quitting for sure, it is good to help by yelling at them whenever they even think about it!  And congratulating them every day they don't smoke.  My MIL quit smoking around our wedding date and reminds us all the time that she's not been smoking since we got married.  She even had a program on her computer that she provided data too (how much she USED to smoke, when she quit, etc) and the program was always up showing all these facts including how many days she has added to her life since she quit, how much money she has saved since she quit.  I thought that was really cool and motivational.

The only other way I can think of to help is to not give in to your friends when they want to go to the smoking section!  Too many people are willing to sit in smoking sections just to please their friends, I'm not, I say Non-smoking right away when I walk in.  I also stopped going outside with my friends when they want to smoke.  Why should I stand out in the cold every 30 mins b/c you HAVE to smoke?  I don't really hang out with anyone who smokes anymore, their loss not mine :)