Coordinate your recipes.
How many times have you done this? You buy a bag of lemons and use one. The rest spoil. You buy a couple great onions, you use a quarter of one and the rest rot in the crisper. If you’re using a small amount of any ingredient, try to think of another meal that utilizes the rest of that ingredient in a different way for the next day. You only need have of a butternut squash for a pasta dish one night? Try Thai curry with squash for the next day.
Just don’t let those unused halves and quarters go to waste. Find a way to integrate them into your next meal to make the most of the fresh foods you’re purchasing.