To train a dogz to catch a boomerang, I prefer to start with the frisbee. So first you take out your frisbee, get your dogz interested in it. After the dogz seems to like the frisbee throw it a few times. Whenever the dogz catches it, reward it, give it treats the first few times, then start petting it whenever your dogz catches the frisbee. This might take a while for some petz, but lots of petz learn quickly.