Credit Cards - Only use if you have the finances to pay them back at the end of the month, being in debt is no fun and can easily get out of hand.
Cash only - Shop with cash I tend to take out my money out of the bank so i only carry cash this way I can keep a tab on exactly what I'm spending.
Make lists - When you budget your weekly/monthly income set aside your maximum amount spend. The average food cost are around £80 per week for a family, But if you are super careful and selective you can properly do it for less.
Meal plan - I go grocery shopping every Saturday so my meal plan is runs from Saturday to Friday, Meal planning helps save on food waste, As you only buy what you need, I try to opt for at least one dish that we can eat more then once in that week eg Curry Dish or Hot Pot
Do I need it - Distinguish between your wants and your needs, We can easily justify that latest purchase, I know this because I've done it, BUT but the big question is do I really needs it.
Don't get drawn in - Supermarkets offer lots of buy one get one free items, but remember if it's not on your shopping list then don't buy it.