What kind of dog do you have? I have seen many people at the dog park I go to who have bought their dog's lacrosse balls. They are harder than tennis balls and bounce a lot more on hard ground. They are also more indestructible. Duncan destroys tennis balls after about one good day at the park. He either squeezes them until they pop or takes the felt covering right off them. And if you play in the winter snow or fall mud, they get soaking wet and filthy! I bought him a Buddy GlowBall so we can play ball in the dark. (We go to the park in the early mornings before work and when I get out at 5pm, it's usually dark during these winter months.) The GlowBall is bigger and rubber but he doesn't seem to be able to squeeze it enough to pop it. Anyway, I don't use lacrosse balls for Duncan because he's very big and I'm scared that they are a little too small for him but a friend has a springer spaniel that loves them!! I don't know how to teach them to fetch except to tell them to come after they have the ball.... When I first got Duncan, he didn't seem to know how to play "with" people. I rescued him from the pound and I think he was neglected as a puppy. He loved to play but for the first few months, he played alone. He would just pick up the ball or toy and throw it to himself (like in the air or roll it along the hardwood floor and pounce on it!)I don't think he knew how to play "with" someone. He learned fast though and now he barks at me if I don't get on the floor with him and play along!