Think of it this way...those clips are composed of two parts. A male and female. Pull the male part (the little screw type thing with a flathead groove in it) half way out. Then the whole clip should fall out or be able to be pried out with a flathead screwdriver.

Be prepared to buy a few new ones, some are really stuck, you and might have to break them to get them out. (or severely mutilate them).