I learned a trick from my Mother on how to keep fabric square by pulling 2 threads at the top of the fabric and cutting it on the line it makes. Then after that when you measure the fabric in strips it will be fairly acurate.

Interesting.

OK I just tried pulling two threads from a piece of Moda fabric. They won't pull out easy, I broke one thread.

That is how I learned to square up fabric in high school sewing class.
I've tried it from time-to-time with my quilting cotton, but have found the threads too tightly woven, or too thin, for they just keep breaking.
Now I just fold selvage to selvage and move them from side-to-side until my fold is flat to square up fabric.

I do as b.zang does by folding selvage to selvage until my fold is flat.

It is a neat way to do it when the fabric will let it happen.

I learned the pulling a thread trick when I worked for a professional seamstress. We used it when making anything that needed to hang just right like curtains etc.

I tear and then cut off a little.

Me too! My grandmother did it that way.

Somewhere in Alabama!

I always tear when doing my backings and get them square. I had a friend who said you never tear it distorts. I said ya do not tear in piecing but for backing, it is the best way to get it square for the frame. Same friend who is a thread snob so I pay her little mind sometimes.