In business situations, use formal titles unless the people you meet tell you otherwise. To get someone's attention you can say: "Excuse me, Sir" or "Pardon me, Madam/Ma'am." To greet someone you can say: "Hello Sir" or "Good morning, Madam/Ma'am."
在商業(yè)場合，除非對方告訴你不需要用敬語，否則就得用正式稱呼。當要引起別人注意時可以說"Excuse me, Sir"或者"Pardon me, Madam/Ma'am."；在同別人打招呼時可以說"Hello Sir"或者"Good morning, Madam/Ma'am."

Here are the formal titles English speakers use:
英語國家人常用的正式稱呼：

1. Sir (adult male of any age)
Sir（任何年紀的成年男性）

2. Ma'am (adult female - North American)
Ma'am（成年女性——常用于北美）

3. Madam (adult female)
Ma'am（成年女性）

4. Mr + last name (any man)
Mr + 姓（任何男士）

5. Mrs + last name (married woman who uses her husband's last name)
Mrs + 姓（用丈夫姓的已婚女性）

6. Ms + last name (married or unmarried woman; common in business)
Ms + 姓（已婚、未婚女性皆可，常用于商業(yè)場合）

7. Miss + last name (unmarried woman)
Miss + 姓（未婚女性）

8. Dr + last name (some doctors go by Dr + first name)
Dr + 姓（也有一些醫(yī)生是用“Dr + 名”稱呼的）

9. Professor + last name (in a university setting)
Professor + 姓（用在大學里）

補充：

The phrase "Yes, Sir!" (or "Yes, Madam/Ma'am!") is sometimes used by native speakers in a sarcastic way. For example when a young child tells his father to "close his newspaper" the parent might say, "Yes, sir!" and laugh. You might also hear a mother saying, "No Madam/Ma'am" to her daughter's request for something unreasonable.
"Yes, Sir!"和"Yes, Madam/Ma'am!"這兩個表達有時會被英語國家的人用來表達諷刺的意味。比如一個小孩叫他父親不要看報了，父親也許會說"Yes, sir!"，然后大笑。你也可以聽到母親對提出無理要求的女兒說"No Madam/Ma'am"。