Stay the hell away from: HFCS - high fructose corn syrup Any prepared food with preservatives Potato or other chips made with cheap, low-quality oils Juices from concentrate Seafood on Sundays and Mondays
Use the Fooducate app to quickly research healthier alternatives to junk food and snacks with too many simple carbs, cheap oils, etc.
As a rule, the fewer ingredients, the better.
Make your own food as often as possible - it's an enriching experience that lets you experiment with new ingredients constantly, home your technique, have guests over for dinner often without embarrassment, and saves you a LOT of money. If pressed for time, make lunch once a week and pack it away in the freezer until the night before you take it to work. It tastes just as good, warm from the microwave.
Cook on/in stainless steel or copper pots, not aluminum. Eat and serve food with silver or stainless steel or copper or other non-aluminum utensils. Aluminum is bad news in your body, especially your brain. And it gets there easily by rubbing off while you put it in your food and then mouth.
Own a solid variety of (at least relatively fresh) spices and use them regularly while cooking! You'll be enriching your food with new and interesting tastes, while supplementing your food with much-needed anti-oxidants, vitamins and minerals. Yes, spices do go stale and lost potency, so don't keep them forever (even unopened).
Eat salad at least 4-5 times a week, if impossible daily.