Believe it or not, a major mistake that people brand new to OAMC make is that they do at least some of their grocery shopping the day of their big cooking session. And this is a big mistake. The last thing you want to do on your cooking day is have to add time (and stress!) of doing a big grocery shop on the morning of your cooking day.
You should also avoid grocery shopping on cooking day, because shopping usually takes much longer than anticipated, and you don’t want to worry about having to go to a second store to find ingredients because the first store had a loss leader on canned tomatoes and were sold out, and three of your meals you planned to cook that day needed canned tomatoes.
Ideally, you should pick up your groceries (always, always, always use a list, otherwise you will find you have forgotten crucial ingredients) a few days before hand – or even the weekend before if you have a chunk of time to do it. If you shop the weekend before, buy the non-perishables only (sauces, frozen veggies, noodles, etc) or the ingredients that would normally last until the next weekend, such as carrots and peppers. Then a day or two before you do your cooking, buy the perishables such as fresh veggies and meat.
Don’t forget that pre-cutting veggies can be a huge timesaver on your cooking day!