I remember learning how to square up fabric for clothing. You'd tear each side so that you'd have it with the weave. (or pull a thread and cut if tearing wasn't a good choice) Then hang it on the fold and see if the ends line up. Usually not, so you and a partner each grab the shorter corners (will be opposite -so across grain) and then PULL and check, and kept it up until you've got the grain running straight.
At least with quilts, off grain is rarely a problem, but if cut pant legs or a skirt out of off grain fabric, it's rarely going to drape correctly.
A lot of fabric gets stretched off grain in the process of dying and winding on bolts. The thing to remember, is after it's washed and relaxes, the fabric will want to go back to straight grain if gravity is pulling on it. Not fun to have your nice pair of dress pants start to have the side seam pull around to the front, and your center crease line have a nice wave to it.
Dealing with fabric for quilting is so, so much easier!
Last edited by Macybaby; 09-02-2015 at 10:27 AM.