The techniques to prevent wastage of food are
(1)firstly think how much you can eat and therefore,how much you might need.
(2)we have to add preversations to the food items so that they would stay for longer time
(3)we can even roast or boil the food without any material like salt so that they would stay for longer time
(4)always segregate your organic waste so that it would not go for nothing when you throw it away
(5)you can use to place the food items in colder place then the colder region would not allow the bacteria to grow on food item
hope this helps you