How much food should I put down for my dog each day?

He's about a 10-15 pound Schnauzer in that range. His diet is mainly Hamburger, Chicken, or sausage I coook with brown rice and occasionally mix carrots, potatoes and other vegetables in with the meat. I give him a large bowl full everyday and he always acts hungry. I don't want to over feed him, keep in mind he's a hyper dog and gets to run around. I'm just curious because I have to drive about 50 miles 100 miles round trip to see a veterinarian. So he's only been there twice in 3 years. I give him comfortis chewable for fleas so he has no fleas or ticks. Any suggestions?