Speak slowly. Marilyn's way of doing this made her adorable as the dumb blonde, but the cagey actress also knew that slower speech can make a character seem either deliberate or vulnerable. An actor who speaks slowly can appear as if each word, thought or line of dialogue is occurring in the moment, made up as it comes out, so that the actor appears in process all the time, never settled. Feel each word as it forms in your mouth and enjoy the feeling; this gives you a subtle sensuality as well.
Throw your head back. Marilyn did this often, frequently combining it with smiles and laughter, conveying both defiance and an insouciant joie de vivre. Marilyn's was a new kind of sexuality for American film, raw yet playful. Reducing the gesture and doing it on a smaller scale may seem to convey, "I am standing up for myself no matter what."
Smile with your mouth open. This lets you breathe while smiling, releasing every possible bit of tension and getting maximum wattage out of the smile. Marilyn taught the open-mouth smile to actress Shelley Winters, who used it to great effect in photos.
When smiling with mouth open, just be sure not to show both sets of teeth, which connotes aggression in both animals and humans.
Weave laughter through your words. This disarming breaking up of words with laughter makes a person seem approachable, not full of herself, and makes her seem surprised by her own mirth. Marilyn's signature giggle, infectious and seemingly uncontrolled, did much to establish her as the icon of accessible, all-American sexuality.
Blink slowly. Audiences love to see a character processing information and reacting right in the moment. A slow blink makes it seem as if you are taking the time to let your circumstances sink in; it makes them eager to know what emotion will appear on your face yet. Marilyn was a master of the true star's technique: drawing out the process of emoting, so those watching could see every iota of reaction on her face.
Soak up everything with your body, and let the effects show. Disappointed, Marilyn slumped completely; intrigued, she inched forward; excited, she wriggled; hot or cold, engaged or angry, Marilyn let her body react. She let the feeling of everything in her environment really sink in. Watch her negotiate a piano bench in "The Seven-Year Itch" or a train's sleep compartment in "Some Like It Hot." She hid nothing physically, an instructive habit for any performer to emulate.