Start with a foundation chain (ch) of the required length.
Yarn over (wrap the yarn over the hook).
Insert the hook into the specified chain (typically the 3rd chain from the hook for standard double crochet).
Yarn over again.
Pull up a loop (you should have 3 loops on the hook).
Yarn over.
Pull through the first 2 loops on the hook.
Yarn over.
Pull through the remaining 2 loops on the hook.
Repeat the steps for each stitch across.
For the next row, chain 2 (counts as the turning chain for double crochet).
Work double crochets into the appropriate stitch of the previous row.
Finish by cutting the yarn, pulling it through the last loop, and tightening.