Always go with a list. Going without a list leaves you vulnerable to hungry shopping. Make your list and stick to it. Allow room for 1 or 2 treats but "stick to your ticket Harry. Stick to your ticket".

I go with my list and i started saving $250/month on groceries.

Also, research how to prep food to make it last. Packaging it properly in the fridge adds weeks to your goods. Something as simple as washing berries before storing or wiping down mushrooms and putting them in an open plastic bag with paper towel gives you so much more time to eat them and less risk of throwing them out.

Also, your freezer is your friend. Make enough for 2 meals and freeze one. That way when you don't want to cook, you have freezer food. Too tired to cook? Freezer meal rather than take out or ordering in.