Plan your shopping in advance and be careful with special offers.
Prepare weekly menus, check what food you still have in your cupboards and only buy what you really need. Choose regional and seasonal products, as they have not travelled a long way and are therefore fresher and better for your health and for the environment.
Buy reduced-price, short-dated food only if you are actually going to eat it. Only choose special offers where you pay less by buying more (such as 3 for the price of 2 or 20 % extra free) if you actually need all of it or if you can freeze the product. Otherwise, you will waste money as well as food.