How can I set up my camera so someone else can quickly take a usable photo of me?

Yes: simplify the camera as much as possible before handing it over.

Good options from the community are:

• Use P mode or A/Av mode with a reasonably high ISO so the camera won’t choose a shutter speed that’s too slow.
• Choose center AF point and evaluative/matrix metering.
• If the scene and distance won’t change much, you can pre-focus and lock focus/exposure before passing the camera over.
• If your camera supports it, Live View with face detection can help, especially for people more comfortable using the rear screen than the viewfinder.

A practical setup is: raise ISO, use aperture priority or program mode, leave flash in TTL if needed, and keep focusing simple.

The shortest useful instruction is something like:

• “Put us in the middle, half-press to focus, then press fully.”

Another helpful trick is to take one example photo first and say, “Please make it look like this.” That often works better than explaining photography in a hurry.

You can improve the technical odds, but composition and timing will still depend on the person holding the camera.