Herringbone stitch, often called Catch Stitch, is a most useful little stitch to know. I use it primarily as a hemming stitch however; it has many other applications. As you can see from the below diagrams, it is a version of Back Stitch, in Cross Stitch form. If using for a hem, only pick up one of the fabric threads on each stitch (a), & it will be strong yet almost invisible from the front of the garment(b). The examples above I have completed in black & white, so you can imagine how the stitches disappear when executed in a complementary colour.
1. Illustration from http://www.french-knots.com/
2. Example from http://bigbgsd.blogspot.co.uk/