How to prepare for The Mandalorian?

You shouldn't have any problem keeping up with the storyline of the show if you haven't watched a single movie in the Star Wars franchise. It has a new set of characters and plot elements.

As the director, Jon Favreau, said,

“It’s an invitation into [‘Star Wars’] in a very pure way,” said Favreau, whose Disney credentials include directing “The Lion King” and “Iron Man.” “It’s the first time since ‘Episode IV’” — the 1977 original — “where it’s inviting people into a whole new cast of characters that doesn’t require any prerequisite understanding of the world.”

I have watched three episodes and it doesn't seem like you have to watch any Star Wars movie before that. The first episode kinda explains everything you need to know.

However, you can have more fun watching the show if you have watched Star Wars movies. On the basis of episodes till now, I suggest you watch the original trilogy which shows the fall of the Empire and has appearances of a Mandalorian, Boba Fett, and an important character.

There is a lot of homage to the previous two trilogies and even elements from Rogue One and The Ewok Adventures too, but that doesn't mean you can't understand or enjoy the story, as it features new characters, but rather you might just miss out on some of the easter eggs (allusions and references), which may help lay the foundation for some of series potential plots and/or could make the mysteries, such as "The Child" more exciting by having some universal knowledge.

With that said, the plot so far tends to dance around things pertaining The Clone Wars era of the prequels, as

There are flashbacks that feature Clone Wars Super Battle Droids that relate to the main character's past, hints about one new surprise character might be a clone of another character or that he might become cloned or used in cloning! The main character has more in common with the likes of Jango Fett, then say adult Boba Fett, even though there are references to him too, but Boba Fett is an unaltered clone of Jango Fett and both have been "ousted" and are not considered true Mandalorians by mainstream Mandalorians!

I think Attack of the Clones & The Clone Wars TV series are important to the plausibility of the series' plots so far.

But I also think given when (five years after Return of the Jedi) and where (The Outer Rim) this series is set, and given that there are characters like The Client & Moff Gideon that are acting as remnants of the Empire, that this may also relate to some of the backstory to the sequel trilogy (The Force Awakens, The Last Jedi, The Rise of Skywalker), as

We may speculate that Emperor Palpatine survived in Unknown Regions of Space via genetic mutation, cloning, and dark side Force alchemy; and he has built two armies: The New Order and a secret Sith army, but in order for this to happen, there have to be people that helped him...Sith Loyalists and the The Sith Eternal.

In Addition, Star Wars Rebels characters could appear eventually, as Dave Filoni works on the series and Mandalorian culture is one of the highlights of this series through one of the main characters, Sabine Wren.

Sabine and/or Thrawn seems likely to show up at some point given one is another well-established Mandalorian and the other could be a key player in a certain character's (mentioned above) survival, but as Jon Favreau has suggested, it's meant to appeal to "all flavors" of Star Wars.

Jon Favreau, - EW

“I don’t want to talk about anything that might be fun for people to discover. We do have conversations. Part of what’s fun to see if we could merge the worlds of the original trilogy, the prequels, the sequels, The Clones Wars, and what’s been considered canon up to this point and what’s been considered part of Legends. I think this show offers an opportunity to bring in all those elements so no matter what your flavor of Star Wars ice cream you like there will be something to enjoy. But you’re asking the right questions.”

So, how to prepare?

I think watching Attack of Clones, having some knowledge of The Clone Wars TV Series, knowing how Star Wars Rebels ended for Ezra, Sabine, and Thrawn, and watching the Original Trilogy will probably be the best way to prepare, but in all honesty, Star Wars fans are pretty good about helping out and pointing out all the references along the way!

You really just need to find a good blog site or YouTube channel.:)

UPDATE: January 5th

The second season has now introduced four previously well-established characters, two of whom are getting spin-off event series that will all build to a bigger story event with later seasons of The Mandalorian and new series, Rangers of the New Republic.

Those characters are:

Bo-Katan Krayze (Clone Wars, Rebels), Ahsoka Tano (Clone Wars, Rebels), Boba Fett (Attack of Clones, Clone Wars, Original Trilogy) and Luke Skywalker (Original Trilogy, Sequel Trilogy)

IMO, this makes having some knowledge of these characters MUCH MORE vital in understanding both the current plot(s) of The Mandalorian, such as the recant history of Mandalore (and by recent I mean, the last 50 years or so) and the legacies of a current Jedi and another one who left the order quite a while ago, but both whose story relies on Anakin Skywalker/Darth Vader. Although their pasts' may be more vital to the spin-offs. Only time will tell.

Keep in mind only a few episodes have been released so far, so any answers may need to be updated to suggest more necessary reading/viewing if any subsequent episodes make additional/substantial references.

While I agree with AJ's answer that you can enjoy the series without having seen any of the movies, there are some rough references to events, plot devices, or entities from past movies that you might have difficulty understanding if you have no reference point.

In general, you should understand the concept of a space western or space opera as those are two genres that "Star Wars" movies/TV generally operate under. The Mandalorian is no different, though it focuses on a bounty hunter rather than Jedi (an organization of quasi-magical, dogmatic warrior monks). If you are a fan of anime, Outlaw Star, Trigun, or Cowboy Bebop would provide perhaps the closest comparisons to The Mandalorian thus far.

Specifically, there are heavy references to the armor and history of the people known as the Mandalorians in the show. For that, you can spend 5 minutes reading this page on Mandalorian armor, which details not only the history and worth of the armor that makes Mandalorians so fearsome, but also provides links to info on Mandalorian culture/history as a people as well (if you are so inclined).

Additionally, you will likely want to understand the concept of the Force, which is arguably the basic unifying plot device of the Star Wars universe in general. In simple terms, it's a sort of magical power that allows, through a combination of willpower and your genetic heredity, telekinetic manipulation of reality. You can choke someone from afar, you can lift a rock and hurl it at someone, you can make some people genuinely believe even an obvious lie, and much, much more. There have already been multiple scenes and one major plot device that revolve around the Force in three episodes (though they don't make reference to the Force explicitly).

Beyond that, anything you learn is likely just icing on the cake, in my opinion.

To me the best part about The Mandalorian is exactly what you are experiencing: Something completely new, though I have watched all the movies. I hope this will make sense:

Star Wars is successful for many reasons, but a core one would be it's wide universe which isn't explained. When people watched the original Star Wars (Episode IV), aside being amazed by the production and characters, they asked themselves what the mentioned clone wars were, how Darth Vader killed Luke's Father, and how this Oh so evil empire came to be.

That's what makes Star Wars great.

Yes, The Mandalorian has references to a great many things. References work both ways though.

Do not watch anything before Mando. IF Star Wars works, the show will spark your interest in watching the rest. You just have a unique Entrance to a bigger Universe which only a few share (at least that's my understanding).

Then you can even say, 'Oh, just like in The Mandalorian'. And to anyone who wants to "correct" you, just mention that neither Mando or Boba Fett would care at all which helmet you saw first. Someone here mentioned you could have more fun with having watched the movies. Untrue imho. Again, works both ways. You could have more fun with the movies by watching Mando first. But that's a discussion for another day.

chronological occurrence does not matter at all.

You shouldn't do any homework for watching a show.

Have fun, I hope you like it :)