It's Black Friday today – but this is the one trick you need to learn before buying anything

Okay, people, don't panic – but it's finally here. After about a month of build-up and at least a fortnight of widespread deals, today is Black Friday at last. That means a swathe of new deals have gone live at plenty of retailers online, including a whole heap of discounts across tech, home, active and more sections.

Before you go haring off into the online wilds searching for bargains, though, let us give you just one single tip that should completely change how you shop online (for the better).

It's not a revolutionary one, unless you've never really done it, but I'd say it's the single most important thing for people to do during sales like Black Friday: use a price tracker.

These simple online tools come in a few different shapes, but each one does the same thing; it gives you an overview of how the price of an item has fluctuated over recent months or years, crucially letting you see if the so-called deal being offered is actually any better than the usual.

These trackers don't work on every online retailer, though – in fact, most of them focus on Amazon specifically since it's the biggest and most popular site. Below you'll find links to three different options, including my personal choice, Keepa.

• Keepa
• Camelcamelcamel
• Bobalob

In Keepa's case, what makes it so useful is that it has a Chrome or Safari extension you can install. This adds a simple graph showing the price over time to each and every Amazon page you visit (in your browser, not the Amazon app), making it possible to do this key research as you browse rather than in a new window.

Others like CamelCamelCamel and Bobalob have other advantages, though, from alerts you can set up to, at times, more robust timelines of pricing.

No matter which you pick, though, this one simple step will change how you see online sales. The truth is that a lot of deals on Black Friday (or Prime Day, or the Boxing Day sales) aren't actually deep reductions because the previous prices were already low.

That's why writers like me use price trackers non-stop, so that we can pick out deals that are actually worth your attention and filter out some of the noisy but fake offers. I'm not necessarily trying to cut myself out as a middleman, since we'll be handy to point you at the best deals, but making price tracking part of your default buying journey is a must.

Make sure you fold it into your routine this Black Friday weekend: it could easily save you from a dud deal or two.