An extra stitch within a corner can give best results for a crisp squared corner.
TIP: Use a presser foot with a clear window to see stitching guide.
Mark pivot points for a helpful stitching guide.
Stitch almost to the point. Stop. Insert needle into fabric.
Raise presser foot, pivot fabric. Lower presser foot.
Stitch one or two stitches. Stop.
With needle in fabric and presser foot up, pivot. Lower presser foot and continue stitching seam.
Trim corner and seams.
Turn and press.