Next weekend American actress Meghan Markle will live out the dream of every girl — well, perhaps not every girl, but many girls — and marry a prince.

Key points: Shellfish is indefinitely off the menu because it poses a higher risk of food poisoning

Shellfish is indefinitely off the menu because it poses a higher risk of food poisoning Markle won't be able to sign autographs and has closed her social media accounts

Markle won't be able to sign autographs and has closed her social media accounts She must always carry a black outfit when travelling in case a prominent person dies

Prince Henry of Wales to be exact: aka Prince Harry.

It's not the first time a commoner — or an American — has married into the British Royal family and like those before her, Meghan will need to master a plethora of royal protocol once she becomes a duchess.

In fact, there are quite a few things that will be no-nos once Meghan says I do at St George's Chapel.

Here are our top 10:

1. No plunging necklines, she must always wear stockings!

Meghan Markle won't be allowed to wear anything as saucy as this number after May 19. ( Source: Instagram/Meghan Markle )

Royal attire is strictly conservative. Necklines are high and hemlines are low.

As an ordinary member of the public, Meghan embraced short skirts, plunging necklines, and, let's face it, wore whatever she wanted.

The Suits star has been allowed a little growing room on her journey from actress to duchess but, one by one, her royal fashion faux pas have been scrutinised, criticised and ironed out for good.

Harry and Meghan's first appearance together as a couple at the Invictus Games in Toronto. ( Reuters: Mark Blinch )

At first glance, this might seem like a cute snap of the couple, but Meghan won't be wearing those jeans again.

Members of the Royal Family are permitted to wear jeans only on dress down days — for instance when walking dogs — but they must certainly never be ripped.

Even when the happy couple officially announced their engagement, royal etiquette stalwarts were furious at her decision to front the cameras with bare legs.

Meghan ruffled quite a few feathers when she stepped out bare-legged after her engagement to Harry was announced. ( Reuters: Eddie Mullholland )

"You never see a royal without their nude stockings," royal expert Victoria Arbiter told Business Insider.

"That's really the only hard, steadfast rule in terms of what The Queen requires."

In stark contrast, Harry's mum, Princess Diana, was a fan of breaking the royal rules and is understood to have regularly used her clutch bag to cover her cleavage when stepping out of cars in risqué low cut dresses.

2. No social media

Meghan won't be sharing any pictures like these anymore. ( Source: Instagram/Meghan Markle )

Meghan once had a huge social media presence, posting pictures of her travels, her dogs, her social life and many selfies to an audience of thousands.

According to the BBC, in 2017, she had almost 2 million followers on Instagram and hundreds of thousands of fans on Facebook and Twitter.

But entering into life as a royal means she's been forced to leave that all behind, and in January, Kensington Palace announced she had closed all her accounts.

The duchess-to-be will join her new husband, William, and Kate in coming under @KensingtonRoyal who manage all their social media.

3. No selfies or signing autographs

No more of these for Meghan if she wants to stay in the Queen's good books. ( Source: Instagram/Meghan Markle )

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Before she was obliged to close her social media accounts, Meghan was a big fan of selfies and would regularly post them on her Instagram, Twitter and her lifestyle blog The Tig.

Unfortunately, puppy filter or not, the Queen is not a fan.

Royal Correspondent for UK newspaper the Daily Mirror, Victoria Murphy, said this message had definitely been passed on to Meghan.

The Royal Family are also not allowed to sign autographs for fans. This is to prevent anyone from forging their signatures.

This is about the best we can expect in terms of an autograph from Meghan now that she's marrying royalty. ( Reuters/Joe Giddens )

4. No running for office

The Royal family has strict rules against getting involved in politics.

Meghan will have to keep her political persuasions to herself from now on. ( Source: Buckingham Palace )

According to the official website of Buckingham Palace, "The Queen has to remain strictly neutral with respect to political matters" and the other members of the Royal family are expected to follow suit.

"She's got to be more careful about how she's photographed and what she's doing," Claudia Joseph, author of How to Dress like a Princess, said.

"She will have to curb what she says, she's not going to be able to be as political as she was beforehand — and that might be trouble in the future."

Royals are also banned from voting, something that might upset the soon-to-be duchess, who has been known to dabble in political activism in recent years.

5. No more acting

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Before her engagement to Prince Harry, Meghan Markle was probably best known for her role as Rachel Zane in the US legal drama Suits.

Ironically, her final scene saw her character Rachel Zane marry one of the other main characters Mike Ross.

In an interview the pair did with the BBC shortly after announcing their engagement, Meghan said she was embarking on a new career now as a full-time royal.

"I don't see it as giving anything up, I just see it as a change. It's a new chapter," she said.

6. No side projects

Along with ditching her social media accounts, Markle will also be barred from any side projects.

That's seen the demise of her lifestyle blog The Tig.

Soon after Prince Harry and Meghan's relationship became public, she closed her lifestyle blog The Tig. ( Source: The Tig )

She's also given up her roles as United Nations women's advocate and global ambassador for World Vision Canada in order to start her royal life with a clean slate, according to British newspaper The Evening Standard.

7. She must always carry a black outfit when travelling

Meghan Markle must now always travel with a black outfit. ( Twitter: Kensington Palace )

Not so much a no-no and more as royal protocol, this one is to ensure that Royals are always prepared for the death of a prominent figure and can dress appropriately.

It stems from the death of King George VI which happened while the then Princess Elizabeth and Prince Philip were in Kenya and she had nothing suitable to wear.

The now Queen Elizabeth had to wait inside the plane she travelled on whilst waiting for a black dress to be delivered.

8. No PDAs (Public Displays of Affection)

We won't see any intimate moments like this anymore ( Reuters: Mark Blinch )

Rather than being official royal protocol, this is another one where senior members of the Royal family follow the example set by the Queen.

According to HELLO! magazine's royal correspondent, Emily Nash, the Queen and Prince Philip believe that when out in public they are effectively at work, and it would be unprofessional to be seen holding hands or the like.

Ms Nash said some affection might be seen at sporting events or similar outings but not formal events.

"But what about Harry and Meghan's engagement photos?!" I hear you cry.

Well, as it happens, those photographs were considered somewhat progressive for the Royal family.

Harry and Meghan's intimate official engagement photos pushed royal boundaries. ( Twitter: Kensington Palace )

9. No shellfish

Something that will always be off the menu for Meghan is shellfish.

The Queen and other senior royals avoid shellfish because it poses a higher risk of food poisoning than most other foods do.

The family is also advised to avoid rare meats, overly exotic, or spicy dishes and drinking tap water in foreign countries.

10. Walking behind The Duke and Duchess of Cambridge

Royal protocol requires Harry and Meghan to walk behind Wills and Kate at official events. ( Reuters/Hannah McKay )

When appearing together in an official capacity, the Royal family always walk in order of who's next in line to the throne.

Prince Harry is sixth in line to the throne so he and Meghan have to fall in line behind Prince William and the Duchess of Cambridge, who are behind the Prince of Wales and the Duchess of Cornwall (Prince Charles and his wife, Camilla).

They all walk behind the Duke of Edinburgh Prince Philip, Her Majesty's husband, and Queen Elizabeth II leads the pack.