Wait 3 days
When I see something I want, I force myself to put it back, and then I wait 72 hours.
If I am still thinking about it, 72 hours later, then it’s clear I really need or want it.
Assess if it’s a need or a want
In that 72 hour time period, I go through an inventory what I already have.
I think about possible substitutes.
I think about where and when I’d use it, calculating the cost-per-use for a week/month/year including time spent.
Get rid of something
I get rid of something to make space for it.
If I cannot get rid of anything, it makes a stronger case to not buy it.
True Scenario: I want a new kettle
I’ve identified a need that my old kettle broke and I needed a new one.
It was $20.
With that shopping information in hand, I waited a minimum of 3 days (in my case, a week).
During the week, I casually noted how many times I used a kettle.
Seemed to be only when I have tea in the morning.
So I looked for other alternatives: heating water on the stove, or simply microwaving water in a cup.
I experimented with my daily tea by using the above methods.
The stove turned out to be an energy waster, and it was inconvenient.
But microwaving water in a cup for 3 minutes on high worked wonderfully.
In the end, I decided that I didn’t really need a kettle.
I didn’t use it often enough to justify its usage, and microwaving water in a cup works just as quickly.
Conclusion: I have one less kitchen appliance.
This is a really banal example above, and now my microwave is a multi-tasking appliance.
(What did we ever do without them!? Stoves and ovens take so long to reheat anything)
But it actually happened, and now I have one less kitchen appliance to plug in and use.