We don't have a plan that never changes, but we do make a meal plan on the weekend and buy just the food for that plan, and it's usually variations on the same few meals (chilli, bolognese, stir fry, frozen pizzas, fajita kits, stew, tuna-pasta-thing, pasta bake). There's two of us, so we mostly cook for four and either have the same meal two nights running or put half in the freezer and have it the next week so we (by which I mean my partner) only have to cook once or twice during the week.

Mostly we use root vegetables that will last longer than a week in a cold fridge, so we check out how ropey it's looking before doing the food shop, both to add the turned stuff to compost and to inform what goes on the list.