Amy, and Steph,
Thanks to both of you for the good lessons in garment fabric and construction.
One thing that is difficult about evaluating "grain" in knits is that many are knit in a tube so the direction of adding to the material is generally in a spiral. So when this material is cut, it is often impossible to BEGIN straight, and washing makes the distortion worse,
Everyone has probably had a pair of pants where one leg hangs funny or feels twisted, or a top with one sleeve like that. That is a result of being cut off grain.
To add areas you may want to include in "quality inspection" when shopping:
Cuffs and sleeve plackets in blouses - smoothly applied, with the sleeve fabric neatly and evenly pleated or gathered into the cuff so the cuff fits close to your wrists.
Shoulder seams feel more comfortable if they lie just a little in front of the top line of the shoulder on your body. The garment will have a little longer back piece and more room in the back part of the upper sleeve and shoulder.
Collar lies flat with no puckers. The under collar is ideally made of a slightly smaller piece of fabric (as are the underside of cuffs and the inside of the collar stand) so the garment forms a natural curve around the curves of your body. This is how a nicely made man's shirt is made, and women should look for the same quality.
Still, not every quality made garment will fit perfectly as we know. Comfortable and flattering fit can be rather elusive. Quality can be found in surprisingly affordable items
and shops. Try on any possibilty and Good luck on the hunt!