Come up at your starting point, either to one side of your seam or right in the seam line. Insert the needle directly across from the origin point, and come up a little way down and in the center of these two points. From this point, insert your needle directly across in the opposite direction as the previous stitch, and come up in the same fashion as before.
Try some different variations... work 2 stitches in one direction, then work 2 back the other way. Try having a "creeping vine" effect originate from a focal point on your stitching. Experiment!