劳驾。

Use it at the start of a request. You can use it to get someone's attention. It works perfectly when you need to pass through a crowd. Just say 劳驾 and people will usually step aside. You can also use it before asking a question. For example, 劳驾，请问超市在哪？ (Excuse me, where is the supermarket?). It acts like a social lubricant for small favors.

You will hear this constantly in northern China, especially Beijing. Use it when you are squeezed on a crowded subway. Use it when a waiter is busy and you need a menu. It is great for talking to strangers in public. It makes you sound like a well-mannered local. It is perfect for those 'micro-interactions' throughout your day.

Do not use this with your very close friends. It will sound like you are being sarcastic or cold. If you use it with your spouse, they might think you are mad! Avoid using it for huge, life-altering favors. For big favors, use 麻烦你 instead. Also, it is not a 'sorry' for when you’ve done something wrong. If you step on someone’s foot, use 对不起.

The term has a beautiful history linked to old transportation. 驾 refers to a horse-drawn carriage or chariot. By saying 劳驾, you were literally asking someone to move their carriage for you. It reflects the deep-rooted Chinese value of 'politeness first.' Even in a modern city of glass and steel, this 'carriage' talk survives. It shows that you value the other person's effort, no matter how small.

In the south, you might hear 麻烦一下 more often. In very formal settings, you might hear 劳烦. If you want to be extra polite, add 请 (please) before it. Some people just say 让一下 (let me through), but that is much more blunt. Stick with 劳驾 to keep things smooth and friendly.