Single biggest difference I made to CoL recently was to plan a week’s meals before shopping. Now, I go to the supermarket to buy what I need to make those meals, which means that there’s little waste. Before I was randomly buying food that I fancied, spending £100 quid on groceries, then the next day going “crap, I’ve nothing to eat.” I’m now spending a third of what I was, having some really good meals out of it, and not throwing half of it away a week later.
The other gotcha is curbing impulse buying. We’d go to Tesco for a loaf and a bottle of milk and come home with an Xbox game, a USB stick, three tops and a pair of trousers. Which is exactly how supermarkets make their money.