加个微信吧。

You usually say this at the end of a conversation. Just pull out your phone and open your QR code. The other person will likely do the same instantly. It is a smooth, low-pressure way to transition from strangers to contacts. You can add 方便吗 (is it convenient?) if you want to be extra polite.

Use it when you meet a potential friend at a party. Use it with a helpful salesperson at a boutique. It is perfect for networking at a business conference. Even if you just met someone at a dog park, this is the way to go. It is the standard 'call me' of the 21st century.

Avoid using it in extremely high-stakes formal ceremonies. Do not say it to a high-ranking official during their speech. It might feel a bit rushed if you say it within ten seconds of meeting. Also, if someone is clearly in a hurry, maybe skip it. Use your social intuition just like you would back home.

In China, the 'QR code culture' is massive. WeChat isn't just an app; it is a digital identity. Swapping WeChats is more personal than LinkedIn but less intimate than a phone call. It created a 'circle of friends' (Moments) culture. This phrase effectively ended the era of physical business cards for most people.

You can say 扫一下吧 (Let's scan) for a more action-oriented approach. If you are feeling more formal, try 能加您的微信吗. For a very casual vibe, just say 加个微?. Most people will understand exactly what you mean even if you just point at your phone screen and smile.