I like to cut borders the length of the fabric. If the cut width is supposed to be 6 inches, I will snip the fabric at 6.5 inch intervals along the width and tear it lengthwise. I will then press, and trim the extra quarter inch off of each side which may get a bit distorted by the tearing. I've never had a problem tearing fabric along the grain like this. It's kind of liberating once you get the hang of it and so much easier than cutting long strips.