I used to have
to take a list when the DDs were younger. It kept them from asking for extras. I would say "Sorry, hon, it's not on the list."
When they got old enough to take the list and the cart while I stood in line at the deli, I noticed a few extras would pop up in the cart. "Excuse me? That's not on the list!"
"Oh, yes it is!" They showed me the list. Yup, the little buggers brought a pen and added the items to the list.
Now, I don't use a list unless I'm party planning or making a new recipe. DD#2 does her own shopping for her lunches (she does make a list) and I usually do the dinner shopping by seeing what's on sale and go from there.
For items that are must-get I think in my head "4 things -- TP, Milk, Laundry Detergent, Ketchup. 4 things, 4 things, 4 things." Then I get 3 things just fine and stand in the middle of the store, staring off into space like an idiot, thinking "4 things. What on earth was the 4th thing?"
Yeah, maybe I should start taking a list again.