The only things I throw away are he dog ends of salad bags, occasionally half a broccoli or some spinach that has gone saggy. Maybe a yogurt or two from a pack of six, although I would still eat two or three days past its date if it smells ok.
Otherwise I cook from scratch, and we eat the leftovers for work, or dd if she is at home between classes in the day. Big portions of leftover pasta sauce, chili, stew are planned for another meal and frozen. Now ds is at uni and it is the four of us at home I find I still have plenty of leftovers and they have started building up in the freezer. We'll probably do a search the freezer tea a couple of times until it is empty.
It feels a bit joyless the amount of planning in advance we have to do, but I would rather have proper home cooked meals every day even if it is a but predictable, than filling up my fridge cause I dont know what we'll fancy and throwing half of it away.
The alternative is to shop every day or two. That is probably great in terms of food waste/eating fresh but very cash and time intensive way of living