Tailors must be able to visualize the the feathers of a well constructed garment. it seems like simple knowledge to acquire. many peoples who earn great pleasure by well finished garments and there for they must know what a well constructed garment look like. poor work bring no satisfaction.
it's always useful to examine well tailored garment before starting.
Well tailored garment's edges are thin even where you would expect the seams to pile up thickly at their junctions of seams is what all god tailors strive at. There are no bumps or puckers.
Also that the edges all curl slightly inward, never outward. this applies to the fronts' the sleeve vents, the pocket flaps , the revers, and the corners of the collars.