Hi...I am by no means an expert but I myself would never tear fabric...I have found the fastest, easiest and most accurate way to cut it is with a rotary cutter and mat. Just be real careful because it is basically an extremely sharp razor blade. I have used my finger as a stop guard and it hurts!!! Thankfully, I was going slow so no stitches but I have a few good scars. :-) I am sure other more experienced quilters will be giving their input soon.
Have a good night!