The coral stitch is essentially a line of floss held down with tiny stitched knots. You can determine how far apart you want the knots for your decorative purposes. To make the first knot, go into the fabric and take a very small stitch by coming up under the laying down floss
Here is a larger view of what the position of everything should look like:
Now you pull your floss all the way through making sure the needle goes above the lower line of the floss "loop"now pull the needle all the way through...
Here is what my coral stitching looks like - heehee...I need a bit more practice before I use this in an actual project!
For me, this stitch is a hard one to make look even and neat. For some reason, I have trouble with the knotted stitches - it seems like right at the critical "knot forming" second when I am pulling the floss and seeing the knot form, something either in my pulling tension, pulling direction or needle position goes wrong and I come up with an uneven knot. I know it will get better with practice - it did with the bullion stitch :) This stitch is #54 and is in the knotted stitches section of 100 Stitches.