@qwertyuiopasdfghjklzxcvbn Buy in large quantity, especially what you can store for long like pasta, rice, etc.
Buy in season... strawberries in February is not a good idea.
Processed food cost more in general
Buy a small freezer so when the chicken is on sale, take as much as you can. I don't pay more than 10$ /kg for chicken/ground beef or pork and 15$/kg for beef, unless it's a good cut on special... Like 25$/kg for filet mignon...
One thing I do is I never buy anything full price if I can avoid it. I stock and wait for it to be on special when I open the last item... Like condiment, canned food, lunch crap, etc