When you look under the item at the price always check your "unit price"!! (this is just a sample tag I googled to show you want I'm talking about it.)
I was looking for pasta and the "sale" pasta looked like a good actual price but I looked above it and the box (same brand) that was twice its size had a better unit price, so I got the bigger box because it was more for the money! BUT some sale prices ARE better! For example, the smaller bags of rice were "on sale" so I matched the unit price to the larger rice bag's tag and the smaller bag was a better price. So instead of getting a big bag I got the same amount in smaller bags because it was cheaper.
It may make your shopping trip a little longer but I like to think of it as "working for my savings".