When I do my "big" grocery shopping at the first of each month, I go to the commissary, which is about 15 miles from my house. I try not to take any kids with me.
I look at the commissary's website to see what's on sale, and I try to plan around that. I will make up about 30 menu plans, and comprise my list around those menus. I organize my list by the commissary's aisle layout, which is found on their website. (My shopping list is HUGE when I go, and there's nothing worse than having to backtrack with an overloaded, heavy-to-push cart to get one thing I missed.)
I fill in the rest of the month's shopping with local grocery stores. I will look at their websites to see what's on sale too.
I've recently decided that I will try to do my big grocery shopping twice a month instead of once a month. That way I don't overload my cart each time I go. (It takes 2 people to carry out my purchases for me!) This will be the first month I try it, so I'll be interested to see if it helps.