Squeaky toys! My terriers go crazy for them. Make sure they only get it when they come back, not at home etc, and play with it in front of them, really have fun (c'mon, it's not the first time your terrier's made you look like a crazy person!) you want them to want that toy so badly they will drop anything to come and get it. This is the only thing which worked with my Jack russel, thought I'd never be able to call her and see her running.