When you can make the single crochet stitch (sc) with your eyes closed (you can find the tutorial here), you can move on the the double crochet stitch.
Step 1: Yarn Over
You will start off with your chain. Make your chain as long as you need it to be and add two extra chains. These extra chains will act as your first double crochet. Yarn over.
Step 2: Go through the Loop
Since this is your base (the chain is called the base), you will make your first double crochet using the two extra chains you have made. This means you will go through the 3rd stitch from your hook. You only need to do this on your chain; once you reach your first row, you can go into the first stitch.
Step 3: Pull Through
Yarn over and pull through. You will have three loops on your hook now.
Step 4: Yarn over and Pull Through Two
Yarn over and pull through two of the loops. This will leave only two more loops on your hook.
Step 5: Final Step
I bet you can guess what comes next. Yarn over and pull through the last two loops. Now, you will be left with that solitary loop on your hook. This single, lonely loop tells you that you have done your job right, congratulations!
Once you have completed a full row, it should look something like this.
This stitch together with the single crochet stitch opens you up to even more projects. Remember this stitch alone can create really nice looking projects. Just continue making more rows. To make another row, you will simply turn your work and chain two. Continue as normal. Practice and practice some more until you can move on to the next stitch!