I'd recommend you start out with a few envelopes - one for each store you shop at, and then one larger one for your extra coupons. As you collect more coupons, you could expand to an index card box with dividers for different food/item categories.
If you collect coupons like me, you will quickly outgrow an index box and need something more substantial. My solution has been this:
A few months before I got married, my mom made me a coupon box just like hers and gave me some of her coupon stash to get me started.
It has worked wonderfully for me.The individual envelopes were made by using small letter envelopes (No. 6 3/4 - 3 5/8 x 6 1/2 in.), cutting the flaps off, and stapling an index card standing up inside.The envelopes are organized alphabetically with the main categories and then multiple envelopes for each main category.
Something like this:
foil, plastic wrap
And so on. Here are the rest of the categories along with some of what are in the categories and the separate envelopes in parentheses:
Baking (mixes, oil/sugar)
Canned (meat, soup, vegetables, fruit)
Cereal (envelopes for each brand)
Cleaner (all purpose, bathroom, dish detergent, disinfectant, laundry, furniture polish, floor, glass)
Dairy (beverage, cheese, sour cream/cream cheese/butter, snacks, yogurt)
Frozen (beverage, bread, ice cream, meat, snacks, vegetables/fruit/potatoes)
Hygiene (band-aids, deodorant, face, feminine, hair, lotion, medicine/vitamins, shaving, soap)Jelly, Peanut Butter
Paper Products (facial tissue, cups/plates, toilet tissue, towels/napkins)
I put restaurant coupons, other coupons for non-grocery stores, rebate forms, and any receipts on one side of the box. On the other side, I'll put coupons which need to be organized. The front of the box has envelopes for each store I shop at.
When I make out my grocery lists for each store, I put the coupons I'll be using in these envelopes, along with the lists for the store. I always bring a calculator and a pen in my box, too.The size of the container fits into the front of the shopping cart (the child seat section), and if you don't have a child sitting in there, this works well. We usually get the "car carts" at Kroger - the kind with the little car attached to the front - and Kathrynne "drives" while we shop! Kaitlynn is in the sling or the ERGO, so we have space to put the coupon box upfront.
I usually only take my whole box in when I go to Kroger, since I often find extra deals and reduced items that I have coupons for which were not advertised in the sale flier. At Walgreens or CVS, I just pull out the envelope in the front of the box which is for that store and head in. If I find some special deal that I know I have coupons for, I can always run back out to the car and get them.