Double Crochet (dc)

Start a row of chains. For practice do as many as you'd like: 

Yarn over.

Insert hook in 4th chain from hook.

Yarn over and bring a loop through the chain.  You will now have 3 loops on the hook.

Yarn over and pull the loop through two of the loops on your hook.  Two loops will be left on the hook.

Yarn over and pull through the two remaining loops on your hook.  Double crochet (dc) created!

Continue to the end of the chain, inserting hook into the next chain each time.  At the end of the row, chain 3 and turn the work.

At this point, you'll have to follow what the pattern says.  Some patterns will have the chains at the beginning of a row count as stitches and some don't.  In this picture, I didn't count them, so there are chains at the end that you do not work stitches into and you don't count as you go. 

The thing you have to be careful of is when they don't want you to count them and you do, you end up with a much wider end of project than beginning.  The easiest way to avoid this is to just count at the end of each completed row.