|This one might be one everyone in the world knows -- but I sure didn't!
I was making a tablecloth -- at one point, I had to cut down the middle of 3 yards of 88" wide fabric. I had the darndest time the first time I tried -- couldn't quite get cutting line straight, couldn't see the fold line well enough in the pattern to follow it. End result was a very ragged and wavy edge cut.
On to tablecloth # 2 -- instead of cutting down 3 yards, I instead made a short 1" snip in the center of the cloth. I then grabbed the two sides of the cut and gently pulled them apart. The cloth "tore" perfectly down the middle -- it followed the grain perfectly and never varied from the centerline. End result was a perfectly straight "cut".
I was pretty jazzed when I figured this out. Like I said, it's probably a standard thing that everyone in the world already knows -- but it was a complete surprise to me!