Choose loose goods and reusable products.
If you can, visit an unpacked store where you can fill your food in the quantities you really need. Take your own packaging with you. These can be cloth bags, disposable glasses, paper bags, etc. There is no unpackaged shop nearby, so look for alternative products with less packaging in your supermarket.
We only buy milk products in returnable glass jars, for example. They are easy to seal and keep fresh longer. We have also made the experience that especially organic and Demeter products have a shelf life very long after the best before date. We buy cheese in pieces instead of slices. This means it keeps longer. Vegetables can be bought at the weekly market or unpacked at the supermarket. We also make sure that they are organic.
Here too we have made the experience that organic can be stored for much longer - contrary to many other opinions. In addition, it does not have to be washed as thoroughly - so it uses less water - as products from conventional agriculture do to wash off pesticides and other chemicals.