广东话口语只说：吸烟，普通话口语多用：抽烟。书面语用：吸烟。 貌似没见过有“”请勿抽烟“这种提示的。

抽 = to draw out. 吸 = to suck.

告诉你：四川人说成“吃烟”，哈…………。没想到吧！

1.First trick is: “吸烟” is more formal than "抽烟"。They both mean "Smoke" (It's a verb), And “烟” means "Cigarette". “吸烟” is mostly used in public signs like "请勿吸烟" and "此处禁止吸烟"。 "抽烟" is frequently used in daily life. E.g. “我出去抽一根烟”（“一根”is measure word for “烟”. Nowadays in China, you cannot “抽烟” inside the room. It's more polite to people who don't smoke.）or "你抽烟吗？"(When you have dinner with Chinese, after or during the dinner, male friends will ask you before he offer you "一根烟"。) 2.Second trick to tell them: We usually put "吸“and "烟" together as one verb. We rarely split them. In "抽烟"'s case, as in the example, we will use "抽一根烟"（literally means "smoke one cigarette"）or "抽一会烟"(literally means"smoke for a while cigarette"). We may use ”抽“ as a verb and "烟" as a noun to split them up and add some details. 3. Third trick is : “吸烟” means the person who is smoking and also the person who is with the smoking person. So even you don't smoke, if you stay with a person who is smoking, you smoke passively. "抽烟" is a verb that only means the person is actively smoking by himself.

“吸烟“ and "抽烟" have the same meaning. In my opinion, “吸烟“ is more formal than "抽烟" . "抽烟" is used more in oral chinese by people in north China.