Taking stock of what's in your fridge can help you avoid buying items you already have. Keep items nearing expiration within sight, so that you remember to use them.
To avoid tossing stale produce, plan your shopping list in accordance with your consumption habits. Only get what you need for the next day or two if possible.
To avoid throwing food away, portion your plate and take only what you plan to eat. Food left uneaten in the serving dish will make for easy leftover meals.
Always get to-go containers for restaurant leftovers. When you get doggie bags, the leftovers serve as snacks or meals for days, postponing the next grocery store trip.
Most grocery stores avoid sourcing and selling oddly-shaped produce because shoppers don't buy them. To save imperfect produce from the trash, consider purchasing them.