Leave all plastic at home and only use cash. Find every loose coin you have (look in bags, under couch, in pockets etc), bag it up and only use that for purchasing snacks or lunch. If you cannot afford it you cannot buy it. This stops me randomly purchasing snacks when I am out and about.

I am not sure if you are or not, is to eat vegetarian as much as possible. Maybe treat yourself to one or two meat meals a week.

Oh and something else my mum found out. Don't bake in your oven. Not worth it. She was making muffins etc at home and the power bill went through the roof. It was actually cheaper to BUY muffins than to make your own once you factored in the power used.