Decide the shortlist before the sale, not during it
The core problem with shopping a sale live is that the list of "things I might buy" is being generated in real time by whatever happens to be discounted, rather than by what you actually needed or wanted beforehand. A short, specific list written a few days ahead -- named items, not categories -- flips that order. If it's not on the list, a discount on it isn't a deal; it's an unplanned purchase wearing a deal's clothing. The list doesn't have to be long. It has to exist before the countdown starts.
Set a ceiling per item, not just a total
A single overall spending cap for the whole event is useful, but it's not enough on its own, because it says nothing about whether any individual purchase is actually a good use of that total. Pairing the overall cap with a per-item ceiling -- the most you'd pay for that specific item, sale or no sale -- gives you something concrete to check a "before" price and "after" price against in the moment, rather than trusting whatever discount percentage is printed on the tag.
A markdown is not automatically a deal
A percentage off an inflated "original" price tells you almost nothing about whether the current price is actually good -- some listed "was" prices are set specifically to make the "now" price look more dramatic than it is. The number that actually matters is the final price against your own per-item ceiling from the list above, not the size of the markdown. A steeply marked-down item you weren't planning to buy, at a price still above what you'd pay for it on your own terms, isn't a discount you took advantage of -- it's regular spending with better marketing.
The "would I buy this at full price next month" test
If the honest answer is no, the sale isn't the reason to buy it -- the sale is the reason it feels urgent to buy it right now. Genuine deals on things already on your list pass this test easily. Impulse adds usually don't, and noticing that in the moment is worth more than any percentage-off badge on the page.
Fold Black Friday spending into the same total, not a separate one
If any of this shortlist is gift-shopping rather than shopping for yourself, the money still comes out of the same overall gift budget it always would have -- Black Friday isn't a bonus round outside that total, it's simply the week some of that planned spending happens to land in. Log each purchase against whichever total it belongs to (gift budget or personal budget) the same day it happens, exactly the way you would any other purchase in that category, rather than tracking "Black Friday spending" as its own separate, unreconciled bucket.
Fund it the same way you'd fund any planned purchase
Because the shortlist and the per-item ceilings are decided ahead of time, the total cost is knowable ahead of time too -- which means it can be funded ahead of time, the same way any planned expense can. A small weekly set-aside in the weeks leading into the sale window covers the shortlist without needing to come out of a single paycheck, or compete with whatever else that paycheck is already earmarked for.
Walk away from anything not on the list
The single highest-leverage rule in this whole plan is also the simplest: if it isn't on the shortlist, it waits. Not "waits until the price drops further" or "waits until you've thought about it for an hour in the store" -- waits until it's gone through the same before-the-sale planning process everything else on the list did. Most things that feel essential in the moment, under a countdown clock, feel considerably more optional a week later with no clock running at all.