To make rain show up well, lighting matters as much as camera settings. The key idea from the examples is to place a light behind or slightly to the side of your subject rather than lighting from the camera position. A back/side light (rim or hair light) catches the raindrops and creates bright highlights on the rain, hair, and shoulders.

A flash can help, especially in darker conditions. For shutter speed, use something fast enough to keep your friend reasonably sharp, but not so fast that every raindrop becomes invisible or too frozen. Experiment to find the look you want: a slightly slower shutter can show a bit of streaking in the rain, while a faster one freezes it more.

In short:

• Use back or side lighting to reveal the rain
• Try flash if needed
• Choose a shutter speed based on whether you want frozen drops or a little motion streak
• Take test shots and adjust

Afterward, you can also fine-tune the image in editing by increasing highlights if needed.