You want to offer a high quality dog food. Puppy chow is not that; it is full of fillers that you don't want in your dog's diet. There are many natural dog and puppy foods that you should check out. Consider Evo, Buffalo Blue, Solid Gold, California Natural, Karma, and a few others.
Do not leave the food in the bowl full at all times! You want to offer the dog food twice a day, removing the food after about 20-30 minutes or so. This gives the dog plenty of time to eat and offers a dominance picture that you're in control and determine when the dog eats. If you let the dog free-feed throughout the day, you risk obesity and the dog doesn't see that you're in control bc he can eat whenever he wants versus when you offer food.
It may sound mean, but it's actually healthier and a great training method. You could offer about 1 to 1.5 cups twice a day. If the pup looks to be gaining weight, reduce how much you're offering to maybe 1 cup at night and 1.5 in the morning. or 1 cup twice a day. It really all depends on the dog's weight, activity level, and type of food as to how much to offer.