麻烦让一下。

You say this while you are moving. It is not a deep conversation starter. Just catch someone's eye or speak toward their back as you approach. Keep your tone soft but firm. If you say it too loudly, you might sound annoyed. If you whisper, they won't hear you over the city noise. A little nod of the head as you pass by adds a nice touch of politeness.

Use this anytime someone is blocking your path. It is perfect for getting off a crowded subway train before the doors close. Use it at a busy night market when someone stops to take a photo right in front of you. It works great in restaurants when a waiter is blocking the aisle. It is also the standard phrase for squeezing through a busy elevator. Basically, if there is a human obstacle, this is your phrase.

Do not use this if you just want to get someone's attention to ask a question. For that, use 不好意思 (bù hǎoyìsi). Also, do not use it if you are far away from the person. It is meant for immediate physical proximity. Avoid using it with close friends in a playful way, as it might sound a bit too 'stranger-polite.' In those cases, a simple 'hey, move!' in a joking tone is better.

Chinese cities are densely populated. Personal space boundaries are often smaller than in the West. Because of this, 'bumping' into people is common. Using 麻烦让一下 shows you are well-mannered despite the chaos. It reflects the cultural value of 'polite inconvenience.' You acknowledge that your movement is a slight bother to others. This small acknowledgment smooths over potential friction in crowded public life.

If you are in a huge rush, you might just say 让一下 (ràng yīxià), but be careful—this can sound bossy. To be extra polite, add 请 (qǐng) at the very beginning: 请麻烦让一下. In Southern China, you might hear people say 借过 (jièguò), which literally means 'borrowing a way through.' Both are great, but 麻烦让一下 is universally understood and always safe.