I too start in the middle. I run one line of stitching right down the middle both vertically and horizontally. That essentially divides my quilt into four sections and makes it easier to continue. After stitching those initial lines, I check the position of the pins, re-adjust if necessary and continue on by alternating vertical lines and horizontal ones. This method seems to keep the quilting more even and I frequently machine quilt queen sized quilts on my Janome 6500.