If you are trying to maximize your savings, you should stock up when your favorite items are on sale. Most stores run sales in cycles every 5-6 weeks.
So, when items that you use go on sale, try to buy what you will need that will last for the next 5-6 weeks. For example...Last week, I bought 5 bags of Lays chips at Harris Teeter because they were on sale Buy 2, get 3 Free. The total purchase before tax was $8.85 making each bag of chips cost me only $1.77. If I was to buy them at regular price for the next 5 weeks, it would cost me a little over $22. So, I saved over $13 over the course of the next 5 weeks on chips (something my husband can't be without!).
The only thing that would have made this transaction even better is if I would have had coupons for the chips. Then, I could have gotten them for cheaper than $1.77 a bag.
My advice is, stock up on sale items and try to use coupons in conjunction with the sales as well to get the rock-bottom price! If you get to know the sale cycles of the stores you love, you will be pocketing lots of extra cash for your family!