Right. There are some good videos, have you seen any of them?
God I wish I could just show you in person, this is my area of expertise 
I will try and describe it in words.
Imagine I am grabbing a section of hair from the top left hand portion of my hair (left hand as in my left)
I'm holding the chunk of hair in my left hand, the GHD's in my right. Imagine the GHD's are a crocodile. The crocodile clamps his jaws over the piece of hair, so his head is parellel with the ceiling and his jaw is parellel with the floor.
You then "turn" the crocodile so that his jaw is now parellel with the ceiling and his head is parellel with the floor.
You then slowly drag the GHD's down the length of the hair. You don't turn them again or change the angle.
Once at the end, release the curl and sort of twist it gently into place.
I'm going to try and find a video, better than the one I've been posting recently. There must be one!