Meal planning is number 1.
Being strict with what you buy then so you don't buy something you have no plan for.
Learn a couple of meals that you can throw anything into so you can use up veg that are just about to go off. Eg ratatouille, stew, curry, etc.
Buy a recipe book with easy one pot meals for inspiration. I find the Internet just has too much and you need to know what you're doing, plus there's just too much distraction. Sitting with a recipe book and a pen and paper to plan is way more relaxing, IME.