For groceries, let NOTHING go to waste. Eat every last scrap of worthwhile food as if there is a shortage.
We plan our meals a week at a time, based on the following priorities:
#0 - First priority is, of course, to consume all of the previous meal(s) as leftovers.
#1 - What do we currently have that needs used before expiration? This includes vegetables, meats, dairy and other perishable items. This is particularly true for meats, as they are usually the most expensive part of the grocery bill. This is even true for herbs that we don't like to waste, like fresh basil. But the closer it is to expiration, the higher the priority.
#2 - What do we currently have that *could* be used? Dried beans, rice, oats, frozen or otherwise preserved foods.
#3 - What would be most cost effective/what is currently on sale at our grocery store/what is in season? We try to combine this with the ingredients available from Steps 1 and 2 to create meal plans.
#4 - What sort of preparation time do we have available? There are a few days during the week that we have to be mindful of how long it takes to prepare a meal, so our meal plan has to account for it. We have lots of go-to quick meals that we still make ourselves.
#5 - Re-purpose and/or transform anything and everything possible. This includes making stock from poultry carcasses, using pan drippings from roasted or braised meats, turning stale bread into bread crumbs, using over-ripe bananas in smoothies, dicing up a few leftover pork chops for use in fried rice or soups and making VERY creative adaptations of quesadillas, tacos curries and beans and rice. For example, just before writing this I had a broccoli quesadilla because we had one head of broccoli left that was just starting to turn color and needed used.
What this turns out to be is an extremely fun way to cook and prepare meals. It allows and even encourages variety, creativity, learning new recipes and culinary skills and trying new ingredients. I find it a lot more fun than simply following a recipe for a fancy pants dish like coq au vin, and it saves a ton of money.
As a classically trained chef, I think you'll have a lot of fun. :-)