The first thing I learned when I started using a rotary cutter was to start about 1/2" from the edge of the fabric and then cut backwards to the edge and then start cutting forward. This keeps the blade from getting veered from the edge, no nicks on the ruler edge, and releases the fabric tension at the same time. I rarely see anyone do this now but it was taught that way at all the classes I went to for how to rotary cut.