Before buying something, do your homework. If you are buying something new, check online ahead of time to see the reviews of the item you are wanting to buy. Check the prices online to see if the price is good, fair or bad. This is especially a good idea when buying a car. Don't base your decision on emotion. Don't buy it right away. Take 24 hours to think about it before making a large purchase.
If you are buying used, check the items very carefully ahead of time. Make sure the color matches what you want to wear it with. Check for lost buttons. Check for rips or tears. Check well for stains. It is better to find them BEFORE you buy it, then to buy it and find them after the money has been spent. If you are able to try on something, do it. If it doesn't fit or look good, don't buy it. Think about whether you really need it or not. Even if it is a good buy, why spend the money for something when you don't need it. Save the money for something you need at a later time. If you have a smart phone, check to see the value of the item you want to get. If it doesn't work out, is it something that you can easily resell?
Save yourself from "Buyer's Remorse" by following these suggestions.