All stores around here run their sales Wed am through Tues pm/up to midnight. This is what I have experienced in my shopping at Walmart and Sam's Club. Your experiences may be different.
Walmart/Sam's Club
I only get there what they do not make coupons for like milk, lettuce, cheap flour/corn tortillas, eggs, produce, cheap yogurt(Walmart), liquid coffee creamers(walmart) -altough there have been alot more liquid creamer coupons this year and I can usually stock up when it is close to free. Walmart does not take internet coupons. Sams takes no coupons. If I have no coupons for frozen vegs, I will get mine here for .77-1.00 a bag of their brand.