The basics are fairly straightforward if you divide the frame into two halves – the dividing line being the point where the door meets the frame stop.
This leaves a hinge side and a non-hinge side.
The soffit is on the non-hinge side.
Comparing the reveal dimensions, the hinge side reveal will be very small, usually about 1/2”, while the non-hinge side reveal will measure several inches.
It gets easier with practice but dividing the fame into two parts is a giant leap forward.