9 things you should know about Amazon Prime Day, one of the biggest shopping events of the year

Tuesday, July 12 marks the second-ever Amazon Prime Day, a day-long sales event in which Amazon promotes thousands of discounts to users of its Prime service.

Think of it like Black Friday - but in July, and manufactured by Jeff Bezos.

If you're thinking of taking advantage of the many products that'll be on offer, here's a quick rundown of what you need to know.

1. The event starts at 12 A.M. Pacific Time (3 A.M. Eastern Time).

2. It'll be available to shoppers in the US, UK, Canada, Spain, Germany, France, Japan, Italy, Austria, and Belgium.

3. You must be a Prime member in order to participate. Amazon sells Prime memberships for $99 per year - or $10.99 per month - but you can grab a 30-day free trial if you're signing up for the first time. Tomorrow's sales will still apply if you do the latter.

4. Chances are you're already familiar with Prime, but as a refresher, it's a catch-all service that brings with it various Amazon-related perks. 

A membership gets you "free" expedited shipping on various purchases, access to Amazon's Prime Video and Prime Music streaming services, early access to select deals, unlimited photo storage in Amazon Cloud Drive, and a 20% discount on new video games for two weeks after they're released, among several other things.

Generally speaking, Prime is a good deal, but only if you know you'll do most of your shopping through Amazon. You need to buy a decent amount of items - probably close to 20 - for those waived shipping fees to pay the membership back off. Plenty of people do just that, though.

5. A large majority of tomorrow's discounts will come in the form of "Lightning deals," or deals that last for a short amount of time - typically a couple hours - or until the product in question is sold out. These can provide deep price cuts at their best, but they're also Amazon's way of capitalizing on that "impulse buy" impetus, and not all deals are created equal.

6. Along those lines: You'll want to do your research before pulling the trigger on any deal that looks too good to be true. As a former commerce reporter, I know full well that the vast majority of deals you see around the web don't actually offer huge savings. That, or they just promote middling products. If you're ever on the fence, make sure to check price tracking sites like Camelcamelcamel to see if Amazon's discounts are really that deep.

7. Several other online retailers will offer their own sales in an attempt to counter the Prime Day assault. All told, this is a good thing, but you should scan those sites with the same skeptical mindset.

8. It's worth noting that there was a fairly sizable backlash against Prime Day's offerings last year, with many consumers upset over the number of unpopular products on sale, and over how quickly many of the things they did want ran out of stock.

Amazon, for its part, is promising an improved selection this time around, with a higher number of deals, and more inventory behind certain devices like TVs. Still, with the sheer number of products being promoted, expect a lot of white noise, with the occasional genuine bargain mixed in.

9. From a sales standpoint, none of that backlash seemed to matter. The company says it saw 34.4 million items ordered over the course of the day - more than it had on Black Friday in 2014, despite the fact that Prime Day's deals were only applicable to Prime users.

This helps explain why Prime Day is a thing in the first place: It helps drive Prime sales, and on average, Prime members spend a lot of money on all things Amazon. That it comes in the heart of the summer, a time when online shopping is typically sluggish, only furthers its cause. There are plenty other reasons, too.

All that said, there will be good deals tomorrow, and more than a few people will walk away with one. If you plan on taking part, just double check to make sure you're in that group.

Disclosure: Jeff Bezos is an investor in Business Insider through hispersonal investment company Bezos Expeditions.