Basic Food Rules

So I wanted to start by saying that it is not my intention to re-produce the many excellent Paleo/Primal/Ancestral eating templates and diets that are already available to you. Far more knowledgeable and competent authors such as Mark Sission, Abel James, Robb Wolf, Dr Catherine Shanahan, Dave Asprey and Vinnie Tortorich (to name a few) have done a great job of continuing the foundations built by the likes of Dr. Weston A. Price, Dr Robert Atkins, and Dr Loren Cordain, and all have excellent recommendations and material for optimum dietary guidelines based on sound evolutionary principles.

However given the importance of diet I cant ignore it completely, so will instead offer some guidance based on my personnel experience that should reduce your mistakes along the way.

Its fair to say that whatever you goals may be, longevity, a six pack, extreme endurance, weight loss, etc, EATING RIGHT IS THE MOST IMPORTANT THING YOU CAN DO. That's right, all the exercise in the world will be wasted if you're eating a crappy diet. When your mother said "you are what you eat" she was right. When she said "eat your crusts it will put hairs on your chest" I'm pretty sure she was wrong!

But whats the 'right' diet then? Well that's not a simple question to answer and I think the reality is that the 'right' diet depends a lot on the individual, and there's no one size fits all diet, no matter what the marketing would have you believe! So to find the right diet you will have to do the leg work I'm afraid. You will need to embark on your own journey of discovery and experimentation and discover what makes you feel the best, perform to your maximum, and generally be awesome. 

I can help you out a bit though. There are some ground rules that everyone will benefit from so start with these. Then do your research, try things out, learn to listen to your body and feel how it is responding to what you are putting in it, and make your own informed decisions about what your optimum diet is. This self awareness will only be generated by following your own path, making your own mistakes, and growing from them.

So here's the basics. 

1. Current Government dietary guidelines are outdated, based on flawed science and unscrupulous marketing forces. Low-fat is not healthy, nor is a grain based diet, Cholesterol is an essential nutrient (not the bad guy), saturated fats won't clog your arteries, and a vegetarian diet is not species appropriate for humans. Sceptical? Do your own research, the websites listed in my links section will be a good start.
2. Refined sugar is a toxin, try and avoid food with it in it. Refined sugar is great for promoting diabetes, obesity and heart disease but otherwise its not much good.
3. Grains are only really good for one thing, fattening up animals, if you want to be a fat animal then please eat lots of grains, if you don't, then don't. Grains are essentially concentrated calories with minimal nutrients (great if you are in a survival situation but I'll wager you're not!), in fact most contain anti-nutrients which inhibit the absorption of any nutrients you do eat!
4. Vegetable oils promote inflammation starting in the gut and extending into the arteries, nervous system, and everywhere else in your body. Try to avoid them and any foods that contain them (which is A LOT).
5. Any animal (humans included) will achieve optimum health when they eat a species appropriate diet. Feed a Lion meat and you have a healthy Lion, feed a Lion Corn chips and...well you can imagine.  
6. Our genes have evolved over the last 200,000 years to thrive on the diets that we have been eating for the last 200,000 years, through the wonders of Epigenetics we can achieve optimum gene expression by eating a species appropriate diet, and conversely by eating foods that we haven't evolved to eat (as mentioned in the earlier points) we will only achieve sub-optimum genetic expression. 
7. Whilst it appears there were probably significant regional variations, particularly in considering the levels of macro nutrients (Fat, Protein, and Carbohydrates). We have all evolved as a hunter-gatherer species. For the last 200,000 or so years we have hunted the animals and eaten the plants that were available. So sorry Vegetarians but based on my understanding of the evolution of our species I personally don't think that a vegetarian diet is species appropriate for humans.
8. It is extremely hard, if not impossible to recreate our ancestral diet. By all means if you want to go live in the woods and hunt and gather your way to happiness then that's awesome, but for the rest of us lets just try and apply some guiding principles to honour our genetic history. Eat real food. Eat plants that look like plants, and meat that looks like meat, and you wont be going to wrong.
9. Work out, through elimination and reintroduction what foods you can and cant tolerate and tailor your diet accordingly. We are all individuals and we should try and tweak our diets to what works best for ourselves.
10. Become fat adapted. If you've been following a standard diet chances are that most of your calories comes from Carbohydrates. Your body uses Carbohydrates as fuel and needs a certain amount however it can also use Fat. in fact Fat is the optimal fuel for your body however the chances are your metabolic machinery has got lazy and needs retraining. DONT jump straight into a Ketogenic eating program but DO start to work on slowly decreasing your reliance on Carbohydrates and re-training your body to use Fat as fuel (by increasing the ratio of Fat to Carboydrates that you eat) . Everyone will see the benefits of becoming Fat adapted.
11. Work out your optimum levels of dietary Fat and Carbohydrates. Some people will have amazing results by working towards a ultra low-Carb/ketogenic diet, for others this will not work, everyone is different, find what works for you.
12. Don't count calories. The calories in/calories out model works in a test tube but it overly simplifies what is going on inside the human body. when it comes to weight loss its the hormonal effect that a food has that's important, and when it comes to health its the nutritional profile of a food that's important. So instead of worrying about calories instead focus on eating nutrient dense food and satiety. 
13. Don't get stressed over food. If you're currently transitioning to a clean, natural diet from a  grain/sugar based one I would encourage relatively strict discipline initially to help "kick the habit".  But once you've cleaned up your diet, re-calibrated your taste buds, and kicked the carbohydrate dependency, if you really want a meal/desert/treat/etc that's not aligned with your new dietary template then go for it. Just be sure you are making the conscious, informed choice to eat it. Eating around foods (I really want a cake so instead I'll have some nuts) rarely works (you'll end up doing the nuts and then some cake later!) and it's definitely not healthy to get stressed out about food. You'll probably find that once you've cleaned up your diet you don't crave the crap you used to anyway, but if you are out for dinner at that expensive restaurant that does the best Gelato in the area, and you really fancy some, then have some!

I encourage you to apply these basic principles initially, apply a Paleo/Primal/Ancestral template to your diet and then go explore. Do your research, use the links to the authors who have been my inspiration and find out what works for you and what doesn't.