Start with what has to stay fixed
If the ring has a center stone, pavé, a halo or a head already fitted to its stones, those may be areas to protect. The first question is what must not change.
Side pavé is a good example
When the stones sit along the upper part of the shank, it is right to preserve the stone and setting area as far as possible and work in the free area. That way the stone sizes and the setting structure don’t change just because the finger diameter did.
And what about a large size change?
The bigger the gap between the original and the new size, the more the overall proportions need to be re-examined. A resize is not just an exercise in inner diameter; it has to keep the piece a piece of jewelry.
Not every ring can be resized simply
A full eternity, or any repeating structure around the whole circumference, doesn’t necessarily leave a free area that can be changed. Sometimes a new size requires a new stone layout or a redesign.