If you are just learning how to do this stitch, I recommend practicing it on a marked stitching line! I first tried just looking at the picture in 100 stitches and stitching on my fabric without marking a line. I was thinking "I know what I'm doing, this looks simple" - only to find out that the needle needs to follow the stitching line not move to either side of the previous stitch, like the picture seemed to be showing!
This stitch is worked from left to right. First come up through the fabric at the beginning of your stitching line:
Pull all the way through.
Repeat the process and this time the floss will be below the needle again:
Stitch and pull through:
Repeat the process and this time the floss is above the needle and stitching line:
Pull through - now the floss is below the stitching line for your next stitch (this is a slightly different and hopefully helpful viewpoint) Notice that the needle is always on the stitching line!
Just keep stitching with the floss alternating below and above (or left and right) of the stitching line:
If you look at the underside of your fabric after you have done a line of cable stitches, you wil see that you have a really nice, neat line of back stitches!
According to 100 Stitches, the cable stitch is also known as side to side stem stitch. The cable stitch is #3 and is in the flat stitches section of 100 Stitches.