Songs that have a good walking beat and that work with the style of the show, for example if the main theme of the show is summer florals girly you don't want to use a heavy metal song. I was in a fashion show a while ago and the part i was in was all about like hollywood glamour, so we used the song "Glamorous" by fergie, it worked perfectly with the section and it was easy to walk to.
Depends what kind of style of a catwalk you are looking for, if you are having a fun type of walk then "love me" by Beyonce. It's all about the style of walk to decide what type of song goes. I was doing catwalks for a year and it was always decisive on the type of walk the designer wanted. Hope that helps :)