Here is a photo tutorial on how to do a base chain double crochet (these are the same pictures I used in my shells and beads legwarmer pattern) .
1. Start out with a ch3. This counts as your first dc.
2. Yarn over, insert hook through first chain and pull up a loop
3. ch1
4. Yarn over and pull through two loops on hook twice to finish dc
5. For next st (and each subsequent stitch), yarn over and insert hook through ch1 of previous base chain double crochet stitch, pull up a loop.
6. ch1
7. yarn over and pull through two loops on hook twice to finish dc
You can also begin a base chain double crochet in the middle of a row of dc to make arm holes and button holes. To do this, you would yarn over, pull up a loop in your next st as normal, then ch1 to start the base chain, finish that dc, and continue with base chain double crochet. To reconnect to the previous row, when you insert your hook into the ch1 of the base chain double crochet, also insert through the stitch you want to reconnect to and pull up a loop through both loops, then finish the dc as usual. I used this technique in my spiral neckwarmer pattern (for the buttonholes) and in my toddler shrug pattern (for the arm holes).
Happy Crocheting!
