I began my journey into "Paleo" eating as a practitioner of the Zone diet, and I still think of myself as a Zone dieter, even if Dr. Harris calls the Zone "pseudoscientific nonsense." (And I anticipate many a flame and down votes for even mentioning the Zone here).
What I recommend to friends is that you first approach a "paleolithic" level of quality in your diet (first step is taking stuff out -- no sugar or alcohol, no refined grains, no processed foods, nothing that comes in a plastic tray inside a bag, etc; second step is adding stuff in -- quality meats, unprocessed veggies, nuts and seeds, some fruit).
But for those of us who need to watch our weight and who have trouble with satiety I recommend two things: (1) keep a journal recording, impartially, everything you eat and when. Use this tool to track your unconscious eating behaviors and check them. When you realize when where, and why you eat and how it makes you feel, it becomes easier to get control. (2) Starting thinking about the amount of foods you eat each time you eat. When I started thinking about food quantities, I used "the Zone" and it has helped me lose 40 lbs and keep it off for more than a year now.
The Zone diet basically argues that you should eat protein and carbs together, and add fat to fuel activity. It is NOT a simple 30/30/40 ratio system; rather that is the baseline or unmodified "Zone" diet, which I call the "canonical" Zone diet. Athletes are advised to eat more fat for energy. And everybody is advised to experiment with the protein/carb ratio until they arrive at a ratio that works for them. For some people, that means much lower carbs. Robb Wolf has a little article called something like 32 Ways to Skin the Zone which explains techniques for adjusting the ratios of a Zone approach to quantities until the desired outcome (fat loss, muscle maintenance and building, general health) is achieved.
Myself, influenced by the Zone, I try to eat small meals, frequently. I try to make sure that I eat some protein, some added fat, and a bit of carbs every time I eat. And the more I feel like I want to lose weight, the more I limit the carbs. The more I feel like I need energy, the more fat I eat.
The "Zone" rule of thumb is 1g of protein per pound of lean mass per day (for athletes). Less for the sedentary. Therefore, if you are 200lbs and have 15% body fat, that's 185g of protein per day, or about 26 oz. of meat, or its equivalent in eggs (about 28 eggs) etc.
For me, a good rule of thumb for carbs is no more than 150g per day, no matter what. That puts me in a Robb Wolf modified "Zone" diet, not a canonical Zone.
I like to think of limiting carbs as such: it is estimated that the brain can use up 130g of glucose per day on its own, so, if you can keep your intake below that level, you virtually guarantee that your body will start to use lipolysis/ketosis and glucogoneogenesis to fuel other activities. And that can mean fat loss. If you eat more than 130g per day, you are basically looking at elevated insulin for glycogen and fat storage, and a bunch of other problems. To put 130g of carbs per day in perspective, that's 13 cups of broccoli, or about 5 apples.
After getting protein and carbs in line, you then eat enough added fat to support your energy levels and activity. Dr. Harris recommends dairy fat. Others recommend coconut oil. Others recommend nuts. Others recommend rendered animal fats. Others like olive oil. There's a huge debate about fats. Tune out the noise and listen to your body.