Half Double Crochet

To make a half double crochet (hdc), make a chain of your desired length.  Yarn over:

Insert hook into the third chain from your hook:

Yarn over and pull a loop through the chain.  You will now have three loops on your hook:

Yarn over and pull a loop through all three loops that are on your hook:

You have made your first hdc! 

Generally, to turn and make another row of hdcs you will work to the end and chain 2, then turn. 

I like to use hdcs when I want a look/feel that is softer than using a sc, but firmer than a sc. They are a nice in-between stitch.