Noticing how the greatest number of deaths happen due to cardiovascular diseases (such as heart attacks, strokes, etc.) and I seem to be having some heart issues myself, I researched into the causes and found...
http://rawfoodsos.com/2010/09/02/the-china-study-wheat-and-heart-disease-oh-my/
The Chinese study is the only major international study into foods and causes of death/disease to this date, and it found that wheat and vegetable oils were positively correlated with heart disease. It's thought that since wheat was only recently introduced to human society, there is a significant percentage of the population that have a relatively high degree of gluten sensitivity. It produces an allergic reaction in the body which causes inflammation, and it's thought that it is a blood vessel inflammatory responsible for artherschelorosis (Fatty calcium deposits in the blood vessels, otherwise known as hardening the blood vessels). This is one of the reasons why heart disease was otherwise unknown in japanese people, but when they immigrated to America and adopted the diet, the heart attack rates started to reflect America's. (Note, that's no longer true today in Japan since their diet has been partially westernized.)
Modern studies also suggest that cholesterol and saturated fats consumption is associated with heart disease. That basically translates into animal meats (except marine species) and animal byproducts like milk, cheese, etc.;
Taking the two bits of info above, avoiding wheat products and becoming a fish-eating vegan minimizes the risk of heart disease.
In other studies, it's found that sugary and starchy diets increases the peak insulin response, which increases the risk of diabetes. So avoiding processed foods is a good idea.
Also, the *lack* of fiber in food products derived from fibrous foods is bad for you. I suspect that fiber's purpose is to slow down the absorption of sugar and nutrients into the bloodstream thus limiting the insulin response, but that is simply my conjecture. For example, eating apples is healthier than drinking apple juice.
So, in essence, eat foods that are closest to nature as possible (Not crushed, filtered,stripped,.etc), prefer fibrous as opposed to the starchy, and avoid modern foods and especially processed foods. Also, avoid meat, eggs and dairy products.
Calorie restriction is also good one. A study found that people who were twice as heavy were nearly twice as likely to get cancer; not hard to understand why, more mass means more cells meaning more DNA molecules, meaning more chances of getting just the right combinations of genetic errors (i.e., oncogenes are knocked out) that would lead to cancer. It also found that higher weight was associated with an increased likelihood of diabetes, heart disease and quite a few other disease processes.
Exercise is also important, but it's not simply a matter of getting your one hour of exercise and you're good, it's more of the matter of staying active throughout the day. Habitual sitting was found to increase the likelihood of all causes of death.
There was a movie I was watching called "National Geographic: Stress - Portrait of a Killer". Basically, it said that high social status animals tend to have less stress and have better cardiovascular health. The low status monkeys were found to have semi-clogged arteries while the top-monkeys didn't. The low status guys also had more belly fat as stress affects fat distribution.
Movie:
http://www.amazon.com/dp/B001D7T460
Also, a lack of sleep was found to impair the DNA repair mechanisms in the body, heightening the chance of cancer. In particular, not getting more than 6 hours of sleep a day increased the chance of prostate cancer in men by over 50%.
Also, not flossing your teeth is associated with shorter lifespans(By a couple of years) and a heightened risk of cardiovascular diseases. The inflammation of the gum line is thought to be involved some how.
So, keeping it all simple:
Become a vegan, eat fish, avoid wheat, vegatable oils and processed foods(They typically have plenty of both) and prefer foods that are natural as possible, keep your weight down, get good sleep and exercise, floss your teeth and never sit down for more than 3 hours a day. Also, climb to the top of the social ladder and stay there, if you can.
Above all, don't worry about it. Anxiety also increases stress which negates some of the benefits. Also, exercise is an EXCELLENT mood regulator. Once you start exercising, you'll get used to the better mood and you won't notice any effects after a while, but once you stop exercising for a week and then try it again, holy crap, is there a noticeable difference!!
My diet is rice and beans along with fruits and fish. Spices are good, too. Don't know if I can "climb the ladder" or if faking it helps, so I try not to think about it, lol.