How to get the look, the sex appeal, the charisma and the vulnerability?
And, ultimately, how to become the disaster on stilettos that Monroe's life turned out to be?
Kirsty McDuff breezes into a West End cafe having dyed her hair blonde that very morning for Wake Me In The Morning, which is on all this week at Oran Mor, Glasgow.
However, she reveals she is not actually playing Monroe. Or is she?
"My character is called Blonde and is very loosely based on Monroe, says Carluke-born Kirsty of the new play by former Citizens Theatre boss Jeremy Raison.
"It is never mentioned Blonde is actually a Hollywood film star, but we quickly get the sense everyone knows her.
"When we first see her, she is immaculately dressed, she looks perfect. But as the play progresses she spirals out of control with the pills and alcohol she has taken."
Yet, it's clear the play is an imagined scene when Monroe meets President John F Kennedy.
"There is a point when Blonde speaks to (Bill) the man in the room and says Mr Pres … but is cut off."
Why would the writer aim for a facsimile of Monroe, rather than recreate the original? It's easy to work out. When you keep the outline suitably vague there is far less scope for critical comparison.
And the actors playing Monroe and Kennedy do not have to fit the indentikit.
Plus, there is far more artistic licence when re-imagining the relationship between the two.
"I'm not trying to be Marilyn, but instead play aspects of her, and that makes it harder," says Kirsty, who has worked extensively in theatre.
"And no one really knows what went on between the. But it is fair to say what could have happened, and then run with that."
Kirsty began performing life as a classical music singer. "And thanks to some really supportive teachers, that led to acting. I just loved the idea of stepping into someone else's shoes."
However while she is reluctant to reveal too much of what happens between Marilyn and JFK in the mind of the writer, she does say it is all set in Blonde's bedroom.
"It is quite a claustrophobic place and we know she is desperately lonely. She does not want him to leave."
There is a third character in the play, Beech who is 'JFK's' brother, and he tries to prevent what is going on between Blonde and her famous lover.
"I don't want to give too much away and spoil the story for those who come to see it, but what I can say is this is a really great play.
"I came in from work one night with the idea of reading a few pages of the script and then going off to sleep, but I just couldn't put it down. And it made me want to go off and research Marilyn."
Does the play run with the storyline Kennedy had the CIA kill Monroe by faking her suicide because she was such a loose cannon? (Can anyone prove the conspiracy theorists wrong?)
Does Blonde does end up in a bed wearing nothing more than Chanel No 5 with a smiling assassin standing over her?
"Who is to say I'm totally naked?" says Kirsty, grinning enigmatically.
Kirsty, who studied acting in London after winning a scholarship, researched the early 1960s and listened to some of Monroe's radio interviews.
"There is one in which she starts calm and clever and by the end she is drunk and volatile. Listening to that gave me something to hang the character on.
"I don't try to impersonate her voice in this play. But I did become aware she offered up a very different voice to the public from her real voice. She was a very good actress."
So the challenge for Kirsty is in playing a character, who is, in fact, playing a character?
"It is," she says. "There are so many layers to Blonde. But I hope I have got it."
Will she go back to her normal strawberry/ginger colour after the run?
"I don't know. I'll see how I feel at the end of the week … once Marilyn is gone."
Don't you mean Blonde? "Mmm, yes, Blonde," she says, laughing.
l Wake Me In The Morning, Oran Mor, until Saturday. Also stars Ewan Donald and Bill Wright.