The cut-out is automatic, but it can only work with what the camera gave it. Five minutes of care here is the difference between a crisp pillow and a soft one.
Stand square to the vehicle and step back rather than zooming with your feet.
A three-quarter angle looks great in a magazine and makes an awkward pillow: the far end shrinks, and the outline stops reading as the shape people recognise.
Get the vehicle as large as you can while keeping a little space all the way round.
We crop to the subject anyway, so pixels spent on the driveway are pixels not spent on the print. Clipping a mirror or a spoiler at the frame edge costs you that part of the shape.
Overcast, open shade, or the hour after sunrise. Avoid midday sun.
Hard shadows across the body get cut out as if they were part of the vehicle. Deep shade under the arches also confuses the edge, which is where auto cut-outs usually go wrong.
A wall, a field, an empty lot. Anything that is not the same colour as the paint.
A white truck against a white garage door is the hardest case there is. Contrast at the edge is what the cut-out reads.
Tap to focus on the body, then take two or three. Skip the ultra-wide lens.
Ultra-wide lenses on phones are softer and bend straight lines. A slightly blurred photo cannot be sharpened later. Extra pixels are not extra detail, which is why a bigger file does not always print bigger.
Upload straight from your camera roll. HEIC from an iPhone is fine.
A screenshot is the size of your screen, not of the photo, and a re-shared copy has usually been squeezed by whichever app carried it.