When I first learned how to machine quilt, I was told to start In the middle and work my way out to the edge, as this would mean less bulk under the machine throat. Then I attended a workshop at my Guild with a quilter/shop owner. She showed us how to properly pin baste quilts, and stated that if your quilt is sandwiched with lots of pins holding it together, you should be able to start quilting wherever you want. If I am machine quilting and doing a simple cross-hatching across squares or 9-patch blocks, I start in the corner and work my way across, first in one direction, then in the other and this has worked well for me. Granted, I have nowhere near the expertise of this machine quilter, but I have found her tips to be very beneficial.