Sewing Rule: All darts should be stitched from the widest area moving towards the vanishing point.
This is extremely important in ensuring a smooth transition from the dart intake to the rest of the garment surface. A smooth transition at this point means a smoothly applied stitch at the dart's vanishing point. The end of a stitch is always much easier to control, resulting in a smooth precise application. Thus, stitching your darts starting at the widest intake and moving towards the dart's vanishing point(s) will provide the maximum amount of precision in the application process.
If sewing a contour dart, the stitch is conventionally applied in two steps, starting at the widest intake and moving toward each vanishing point. To lock the the threads, the beginning of the stitches are overlapped at the center widest intake.
Note: To avoid puckers and tension at the vanishing point, never backstitch at the end of the stitch. To lock the machine threads you can simply tie them in a double knot. However, you can backstitch at the widest intake, or at the beginning of the stitch, to prevent the dart stitch from unraveling at the seam edge in the remaining sewing process.