You don't really want to copy others girl's walks.(Sorry if I like put others comments down.) The only reason I say that is,each desginer might want you to walk a different way(depending on the genre of style that they do);although,you want to have you OWN style of walk you do. Just partice with basic then spice it up.
For dress,wear something that totally you. Be yourself when modeling unless you are given a role and if they don't like you then it's their loss.(:
If you watch America's Next Top Model(My favorite show from America). Then Miss Jay teaches the girls basic steps and how to improve on walking. What my mom taught me was to hold your head up and don't let others tell you what to walk unless told by the desginers,be proud of yourself to get up there and show yourself off. I hope I help some.^^
Good luck too~ (I only know half of this stuff is because My mom takes pictures of Models and she wanted me to do somethings with Modeling to get the feel of the industry. Meaning she wants me to be one.))