Today you need to do a pantry and freezer/fridge inventory, so that you can see what you have, and what you may need to buy this month. I include my groceries budget in my monthly budget, but this month is all about stretching your existing groceries (and your imagination near the end) just to see what you already have.
You can get a free printable for these at http://www.livingwellspendingless.com. Here are mine from October, since this is on my to-do list for this evening (because I am wild and crazy like that, woo-hoo).
Meal planning is a part of my planning for every week, so that I know what to buy at the grocery store. I have found that this cuts down on my panic shopping, or even picking up fast food for supper on the way home.
You will be surprised at how much food you have in there!