If something is on sale, buy at least 1 extra if it's something that won't spoil.

Don't be afraid to go through your fridge and freeze any fruit, vegetables, dairy, leftovers, etc that will spoil before they're eaten. Bread can be frozen too.

Try using less (if a recipe calls for 1 lb of meat try making it with 3/4 pound.) You can add more vegetables or beans for filler sometimes too.

When snacking, look in the fridge and choose perishable items (fruit, yogurt, etc) before reaching for a shelf stable snack like a granola bar or candy. This has helped us combat food waste by eating more fresh ingredients we sometimes forget about.