A few years ago, late in the day on Black Friday, my wife and I were at Target. We weren't looking for anything in particular, but we ended up leaving with a stack of sub-$10 appliances.

We bought two toasters (the old pop-up kind), two coffee makers, and a low-end handheld blender. One of the toasters still sits on our counter (next to a much-nicer toaster oven), but the other items ended up in offices where we no longer work, and at least one coffee maker was thrown away when we moved to a smaller home.

Spending, maybe $40 on impulse buys did not break our annual, or even our holiday budget, but the event did show how easily things can go off the rails. 

My story is the perfect example of how Black Friday can go awry for shoppers. And if I had walked by a large television or a video game console at what I perceived as a good price, our unneeded, unplanned spending spree could easily have been much worse. 

To avoid the same fate this shopping season, follow the four steps below.

A shopping bag has Black Friday printed on it.

Black Friday can mean getting great deals, but it can also get you in financial trouble. Image source: Getty Images.

1. Have a budget

You can't stick to a spending plan if you don't have one in the first place. That means you have to make a realistic budget for the entire holiday season. This needs to include travels, meals, entertaining, and any other expenses you would not incur normally.

Only a portion of that will go for gifts and, perhaps, only some of that will be spent on Black Friday. It's OK if you move money around in your budget, but doing that requires understanding what your overall spending plan is.

For example, if you plan to buy your son three gifts totaling $120, but find a Black Friday deal on something he really wants that costs $100, you have to adjust your future spending accordingly. It's also totally fine to forego one expenditure for another (perhaps you swap a new TV for an overnight trip) but you need to keep a running tally and make conscious spending decisions.

2. Do your homework

Just because a retailer touts a big discount does not mean you are getting a good deal. One of the biggest challenges of the season is sorting out what you are actually buying and whether you're getting a good price.

The first place to start is looking at the sales circulars and online deals retailers release in advance of the holiday. These can be used to research what the items cost before the sale. When doing this homework, be careful and check model numbers closely. Sometimes companies sell similar items with fewer features at lower prices. That's a particular problem when it comes to televisions and other electronics.

3. Have a shopping plan

Black Friday used to be fairly simple. Stores opened early on the Friday after Thanksgiving with many of the best deals being limited-quantity, first-come, first served deals. For consumers, that meant picking the offer you wanted most and waiting in line at that store early.

Now, Black Friday has leaked into Thanksgiving itself. Some retailers open their brick-and-mortar stores on Thursday evening while others have Black Friday deals go live on their websites during the holiday. That means as a shopper, you need a plan as to when the deals you want are being offered and whether they are digital or require visiting a store.

To further complicate things, while "doorbuster" deals are still offered at opening, many chains sprinkle other offers throughout the day Friday (and sometimes Thursday too). Know where you need to be, when you need to be there, and have a plan that maximizes your savings while also valuing time spent with family.

4. Know when to walk away

Sometimes you don't get the deal you hoped for. That's when, for many of us, mistakes happen.

Maybe you had your eye on a specific appliance offered as a doorbuster sale at a great price. You did your homework, got in line early, and still you don't get the item you wanted.

In a lot of cases, that's when people overspend. They turn their disappointment (and maybe a hole on their gift list) into justification to overspend on something else. 

Don't let that happen. When your plans go wrong, fall back, and make a new plan. It's OK to walk away and preserve your budget to shop again another day.