As a dog is a scavenger, it's natural for them to be on the hunt for food; especially if you're feeding them raw food and they know it's available! =D Often, people assume their dogs are starving if they are always begging; when often the case seems to be that the owner had been rewarding the behavior; i.e. "caving in" and giving a tiny tidbit of a treat so they'd "stop bothering them." Unfortunately, what they've actually done is taught the dog that the longer it persists in any attention (and food)-seeking behaviors, you will eventually reward it. As dogs are very smart, they pick up on this, and will learn very quickly to continue repeating the behavior.
Your dogs weight will be your best indicator of how much to feed them. Just as it is with people, what works for each individual dog will differ based on metabolism, activity level, etc. and it's about finding the right amount for each dog. Also, as raw fed dogs are given bones as part of their diet, it's a lot more mental stimulation as well as they are working their jaws and teeth. I hope that answers your question! =)