If I find people smoking in no smoking areas, how can I report the case to the Tobacco and Alcohol Control Office?

As smoking is an action that lasts for a very short while, enforcement officers cannot arrive at the concerned location immediately after receiving your complaint.  Therefore, you can make a complaint to the venue manager of the premises and request them to take necessary tobacco control actions. 

If the smoking offence persists, you may consider making a complaint to the Tobacco and Alcohol Control Office (Tel: 2961 8823 / Fax: 2575 8944 / Email: tobaccocontrol@dh.gov.hk ).  The Tobacco and Alcohol Control Office will follow up and take necessary law enforcement actions after receiving your complaint.