Well it depends on your dog. If your dog is the kind that will eat and eat and eat just because there's food in his bowl (like mine), then you should limit his food to two/three times a day for a puppy and one/two times a day as an adult. If your dog only eats when he is hungry, then you can free feed (leave food out so he can eat whenever he wants).

I don't free feed my dogs because if I did, my Rottweiler would weigh 200 pounds, not 89. He would just eat and eat forever.