Ask:
There are five of us in the neighborhood that have divided the stores, so we each only shop at one of them. One of us goes to costco, another goes to target, another goes to Kohls, etc. I go once a month to Costco and buy bulk food that is divded. We split the annual membership. Another friend goes to the sales and clearance at Kohl's. She has all our kids sizes and what they may need. This saves us so much money and time. I use to always spontaneously buy things at these stores. Now I just get what I need!
Answer:
I havea variation on this theme ... limit the days on which you shop.
I try to do all my 'in the car' errands on only one or two days of the week. I'm much more aware of what I'm spending when it is concentrated into one or two spending sprees like that. I'm also aware of how much I'm buying! Okay, the minivan is full. It is time to go home.
The added benefit is I delay my spending so I'm less likely to buy something that I really don't need. Instead of running to the store to 'pick-up something quickly', the delayed purchase often ends up being something I've completely forgotten about by the time my 'errands day' rolls around.