A good little terrier pup will work its way through the list rats,rabbits squirrels then it scent old charlie one day and naturally do its thing. Once you to that point you can keep it leaded up and go earth checking. You can't force the issue. In the early days you want things to go the dogs way easily nice shallow earths on braken banks or small hedge row ones so you can get down quick. Just my vague memories of it all