The correct answer to this open question is the following.
The advice that I would give to a friend that throws the food in the waste bin often would be this one.
Hey dear friend, do not throw the food in the waste bin because you do not have an idea of the millions of people that had nothing to eat, not only in our country but in developing and poor countries. And as teachers have told us in class, there are many.
What you have to do is to cook only the food that you are going to eat. Never waste anymore.
Another good advice would be to serve portions of food that you are going to eat, with moderation.
If you have more food than you need, please, share it with other people who are in need. There are food banks in many medium and major cities that gladly would receive your food to help the poor.