Need to stop him now while he's young. Once behaviours and habits are in place it's much harder to do something about it. You need to be firm and consistent. At 6 months, twice daily feeding should be adequate and try to avoid the snacks in between apart from as training rewards. If he begs, ignore him. Put him out of the room when you're eating and get into the habit of you eating first and then feeding the dog. Make him work for his food -use it to train him to sit, lie, stay. Don't leave food where it's accessible on the counter. Keep perservering and you'll get results!