I've started grocery shopping every 3 weeks. Sometimes 4, if I stop by the local tiny store for eggs and milk. I hate grocery shopping, and have been developing an increasingly elaborate system to avoid it. Sadly, my local store is more like a convenience store than a grocery store, with double the cost of a normal store, tiny package sizes, and doesn't stock most things I eat.
I keep a running list on my phone of things I am short of, plus always-buy items.
I put a star beside items I am completely out of, otherwise I wait for a sale. I have started to organize some of it by shop - my tea and international foods comes from one shop, I tend to buy meat at another plus a specific condiment, a third is good for gluten free bread and household goods, a fourth for canned goods, a fifth for dish soap, a sixth for gluten free flour and soy sauce... Etc. Some stores I go to every other trip, others maybe once a year. Some items might end up on a list for months before I buy them. If I list what I tend to buy at those places and grab them while I am there, then I don't have to go back!
If I have an appointment in town, I'll grocery shop then, otherwise, Flyers run Thursday-Wednesday, but you can see the Thursday flyer online on Wednesday. On Wednesday morning, I try to glance at the flyers for BOTH weeks to decide if I am shopping that day, or waiting a day. Then I go into town, and sometimes hit one store, sometimes 2 depending on the sales and what items I am completely out of. Once I'm in the store, I check out in store meat/dairy/fruit sales, and buy whatever appeals. I am a good enough cook I can make something tasty from whatever is cheap that week plus pantry staples. I find it fascinating that I have no interest in 95% of the items in a grocery flyer. When I get home, meat goes mostly into the freezer, usually after being cut and portioned out.
I find I save money this way - I save gas, I save on impulse purchases, and I also don't end up stopping for coffee or a snack as often. A list is critical, otherwise I forget I'm out of something, and end up driving back sooner.
As I do this longer, other than eggs/milk, I often reach the 3 week mark and really am not desperate for anything. I have enough long term staples to last longer, and even milk, I have evaporated and dried milk, so it's not really an issue.
I sometimes go grocery shopping with friends, it really doesn't work well! They want to wander the aisles and get a few things for dinner, while I'm grabbing a dozen cans of tuna and half a dozen pounds of butter because they are on sale, and keep checking a list! I also struggle with grocery shopping with my mom, who wants to walk down every aisle and talk about random things we see, rather than my strategy of shopping the outside, then checking my list for whatever I have missed and ducking into relevant aisles. By the time we have walked every aisle, I have impulse grabbed several things and am WAY too tired to want to bother checking my list to see what I have missed, and inevitably, get home and realize I forgot something critical.