I am posting these 2 stitches together since they are both take-offs of the single crochet. The best way to explain them is to contrast them.
Single Crochet Double Crochet Treble Crochet
ch 1 to turn ch 2 to turn ch 3 to turn
insert hook yo, insert hook yo 2 times, insert hook
yo, pull through yo, pull through yo, pull through
yo, pull through last 2 loops yo, pull through next 2 loops yo, pull through next 2 loops
yo, pull through last 2 loops yo, pull through next 2 loops
yo, pull through last 2 loops
As you can see, the major differences are:
1) how many chains you have to make when you turn
2) The yarn over (yo) step BEFORE you insert the hook
3) The number of loops left on your hook after you do the first pull through.
PRACTICE: To practice these steps, you will also need to adjust your foundation chain.
Double crochet: Instead of chaining 51 and starting in the 2nd chain from your hook, you will need to chain 52 and start in your third chain from your hook.
Treble crochet: Chain 53 and start in your third chain from hook.
On these stitches, your chain 2 or chain 3 will count as your first stitch.
Go ahead and crochet up your squares for your double crochet and treble crochet. Don't forget I'm available to answer any questions you have over on my Facebook page.