Just though I would start a thread of stuff that is often overlooked, especially by me:
Vacuum Filters / Hepa Filters - Makes the vacuum work like new. Buy in bulk and keep some in storage
Furnace Filters - cheap ones come in bulk packages - are the expensive ones even worth the price?
Shop by understanding weight vs. Cost - when is a good deal. Just because something is on sale, doesn't mean it is a good deal. Likewise, when Pork is on for $1.00 /lb. then snatch it up, even if it is $22.00 worth, such as the two large pork shoulders I plan to smoke. Sometimes the most unlikely store has real deals. I bought two cases of Kraft Dinner (Mac and Cheese) each at $6.00 / 12 boxes. Costco doesn't even sell it that cheap and it was at a drug store that tends to be high cost. When you see the deal, act on it.