How to stop buying on impulse

This guest post comes from Andrea Whitmer at So Over Debt.

Not too long ago, I was the queen of impulse shopping. I could go into a convenience store for a drink and come out with two bags of junk. A trip to Target for a shirt often turned into a whole new wardrobe. Oh, and you know all that random stuff in grocery store checkout aisles, like batteries and lip gloss? Yeah, I was a huge fan of that, too.

When I decided to get out of debt, my addiction to stupid purchases was one of the first things I had to control. And it sucked. I had never shopped from a list -- or if I did, I bought lots of things that weren't on the list. Half the time I didn't even realize I was grabbing the items until I got home and wondered how I spent so much money. With that kind of history, I wondered at times how I would ever learn to stop buying on impulse.

Decision trees

One of my favorite images from the Internet is this one, a decision tree that tells us when it's appropriate to use "Oh snap!"

When I was trying to stop impulse shopping, I decided I would make my own decision tree. Since I had so much trouble discerning smart purchases from dumb ones, a decision tree would give me a list of questions to ask myself. The choice would already be made before I even got to the store; I just had to follow the arrows until I got to it. Post continues below.

Choosing the questions

To select the questions I would ask myself before buying something, I had to learn how to prioritize. I wrote out a list of "good" and "bad" reasons to buy something. Then I picked the most relevant ones and ranked them in order of importance. This is the list I came up with:

• Do I need it to live? This puts food, clothing, etc., at the top of the list.
• Do I already own something that will meet the same need? This prevents me from buying McDonald's when I have food at home, or buying a new coat when I already have 10 of them.
• Will it solve or prevent a real problem? I don't need toothpaste to live, but it prevents cavities and bad breath so I'm going to buy it. I may think that boredom requires a new DVD, but that's not a real problem so it doesn't pass the test.
• Will it provide SOME kind of value? Sometimes things aren't necessary but we want them anyway. For example, I bought an Apple TV last year. It allows me to stream Netflix, which made it possible to cut off my cable TV. So even though I don't need an Apple TV to live and it doesn't necessarily solve a real problem, I still decided it was worth buying.
• Can I afford this item without going into debt? If I have to go into debt for something I must have to live, I can deal with that (though I'd rather not). But if it's not a need and I've still decided to buy it, I have to make sure I can do it without pulling out a credit card or incurring overdraft fees.
• Will someone be angry if I buy this? Will I have to hide it or hide the receipt? Now that I'm divorced, I don't have to picture the wrath of a spouse. But when I was married I used to pull the tags off new clothes and sneak them into my closet all the time. (Hint: This is probably a sign I shouldn't have bought said clothes.) These days, I pretend that Suze Orman will be going through my shopping bags when I get home.
• Could my money be better spent elsewhere? Can I really justify buying a pair of shoes if I know my car needs an oil change? What if I need to buy a birthday gift for a friend next week?
• Is the "something else" really important? Am I spending money that needs to go toward bills? If so, not buying. If the money is just earmarked for a competing "want," I'll have to make a choice.
• Do I still want the item after all this? If none of these questions made me give up, I'm probably buying it. For something silly like nail polish, I probably would have given up a long time ago.

Using the decision tree

For a long time, I actually had a handwritten decision tree in my purse. It was more of a list with some haphazard arrows, but I knew what it meant. And I would literally pull it out in Wal-Mart or the mall to decide whether I would buy something that wasn't on my list.

Did I look stupid? Probably. But I didn't feel stupid when my spending decreased dramatically.

I made a pretty version of my decision tree, just because I love you guys. Or you can download your own (.pdf file) to print and use.

How decision trees stop impulse buying

Using a decision tree, whether it's the one above or one you make for yourself, is a great way to keep yourself from overspending. If you're disciplined enough to use it, you'll talk yourself out of a lot of random purchases. For some reason, it's hard to argue with something in writing. And the time you spend looking at your piece of paper is usually just enough time to think about what you're doing.

In other words, by adding an extra step to the purchase process, you are training yourself to stop and think instead of blindly throwing things in a shopping cart. When you're walking around with your decision tree in your hand, you'll remember to think things through.

And, if you're like me, you'll eventually train yourself to go through the process mentally, whether or not you're holding the decision tree. It becomes a habit to replace the impulse-buying habit.

Are your impulses under control?

Most people don't have to put forth this much effort to prevent impulse shopping. They can evaluate the pros and cons of a purchase in their heads in a matter of seconds, making the right choice almost every time. But if you're like me and struggle with nickel and diming yourself to death every month, it's worth a shot.

Have you ever struggled with impulse buying? What steps have you taken to control it? Would a decision tree help you make better decisions?

More on So Over Debt and MSN Money:

• What does your financial behavior say about you?
• How much is $20?
• 3 money mistakes I keep repeating
• Calculator:Is your budget in balance?
• Is eating out cheaper than cooking? 
• Spend on the things you do daily