The nails should really reflect your cuticles
If you are not sure of what shape your nails should have, just look at your cuticles. Think of your nail as an oval—an odd oval. The U-shape of the cuticle should be reflected (upside down) by the top of your nail. And, since the top is often wider than the cuticle, you may have to adjust for size; what we want is to mirror the shape.