Can I immediately think of 3 outfits to wear with this?
Instant outfit planning is always a great sign. It's a sign that you'll get plenty of wear out of the item, making it a smart purchase instead of an impulse buy. And if you can think of more than three outfits, even better!
Do I already own something similar?
If the answer is yes, chances are you don't need it unless it needs replacing. If you're still not convinced, ask yourself if you would be willing to donate something else in its place to get the new item. If that's a no, this item is probably not worth it.
Does it complement the rest of my wardrobe?
While it shouldn't be a copy or variation of something you already have, it should fit in well with the existing mix. This means it will be easier to create outfits, and it will be your style. Sometimes we want to try something a little different, and that's fine. But if it sticks out like a sore thumb, chances are it won't see the light of day very often.
Can I really afford this?
Just because something is a good deal on the tag, it doesn't mean it's a good deal for you. If you're shopping in December, there might be someone else you should be shopping for. If you have to sacrifice anything to get it (like skimping on groceries), forget it. Your necessities are always more important than something you find kind of cute.
Will I still love it in a year? Five years?
This is a big one. Will this be one of your go-to pieces, year after year? Sometimes we buy things for instant gratification just because they seemed like a good deal at the time. If it's something you see yourself getting bored of after a few months, leave it. Finding pieces that you will love for years is the ultimate goal. It reduces waste and helps you build a capsule wardrobe that shows off your signature style.
Being a smart shopper means being a sustainable shopper. Taking a little extra consideration time in the shop will make a big difference in the long run.