A front post double crochet is almost the same as a normal double crochet except:
*Your hook is inserted around the previous row's double crochet (or stitch).
Here are the instructions.
Yarn over hook. Insert hook from front to back around the double
crochet of previous row. Yarn over hook and pull up a loop (from
around your post). Yarn over hook and pull through two loops on your
hook. Yarn over hook and pull through the last two loops on your
hook. Front Post Double Crochet completed.
Look at Figure 1.
The black arrow shows a regular or normal double crochet.
The red arrow shows where you must
insert your hook: from FRONT to BACK, go around the post, then to
the front again; yarn over hook (at the
purple arrow), and then pull out of your stitch. You'll
be going around the post again on your way out.
Look at this picture. You'll notice that the yarn looks like it's wrapped around the double crochet from row 1. Finish your front post double crochet like any other double crochet.
In this picture, you have, from right to left, your turning chain, 3 regular double crochet, two front post double crochet, two more reg. double crochet, two more frontpost double crochet and the last double crochet of the row. See the difference between the two.
TIP: If after pulling out your yarn from around the post and completing
your Front Post Double Crochet (FPdc), you notice that it's shorter than
the others, then do this:
Once you have inserted your hook around the post
and yarn over hook, pull up your loop level with the previous loops on
your hook. They should be the same height now.