Emma Stone - Spiderman's squeeze shows her mettle

For a girl who trades on easy-going charm, Emma Stone's inexorable rise over the past year seems to be the result of precision plotting. This is the actress who, at the age of 15, gave her parents a PowerPoint presentation entitled Project Hollywood, to convince them to let her drop out of school and move to Los Angeles. When casting directors kept sending the naturally blonde Stone for entirely inappropriate cheerleader-type roles, she dyed her hair brown – and then, when she was cast in her first film, Superbad, turned herself into a redhead: anything to stand out from the crowd.

You have to say it's worked. Still only 22, Stone has just seen the back of a remarkable summer. First, there have been two bona fide hits – the Steve Carell comedy Crazy, Stupid, Love (global box office $136m and counting) and The Help, the adaptation of the best-selling novel by Kathryn Stockett that's the sleeper hit of the season (taking $164m in the US alone). Then there was that watershed in any actor's career, a cover shoot for Vanity Fair – in a particularly fetching striped bikini. "It still boggles my mind," she reflects, widening those almond-shaped green eyes. "It feels like it didn't really happen. You think: 'Why me?'"

She even laid the groundwork for what will surely be the biggest hit of her career to date with a visit to San Diego's Comic-Con ahead of the release of next year's blockbuster reboot The Amazing Spider-Man, co-starring Britain's Andrew Garfield as the web-spinning superhero. A veteran of the famed fanboy convention – "it wasn't my first rodeo," she laughs, explaining she went for 2009's horror-comedy Zombieland – she enthuses about the fans who welcomed her casting as love interest Gwen Stacy. "That kind of passion is one of the most fun reasons to be involved with something like Spider-Man."

Then again, since Stone became the object of geek affection in Superbad, she has been a poster child for the nerd crowd, flogging her goofy charms in films such as The House Bunny, The Rocker and Easy A. Her skills as a comedienne have certainly got the respect and attention of her co-stars.

"I remember being with Bill Murray on Zombieland," says the actor Woody Harrelson. "He was like: 'That girl is just gold – everything that comes out of her mouth. An incredible improviser.' It's really rare that you see a really funny, beautiful woman, who really just has the whole package. She's got it all."

In person, Stone is affable and genuine, the sort you can't imagine going off the rails on the Hollywood party scene. But deep down, there's a determination to be taken seriously. Right now, she's filming The Gangster Squad, which purports to tell the story of the LAPD running up against the notorious gangster Mickey Cohen. "I've got my 1949 nails on," she grins, waggling a flash of red. Featuring as a "sharp-tongued siren" caught in a love triangle, it means going head-to-head with Sean Penn, who plays Cohen, as well as reuniting with Ryan Gosling, her Crazy, Stupid, Love co-star. "It's pretty damn cool," she drools, with good reason.

Still, it's The Help that has proved Stone as more than just a comic star. Featuring a predominantly female ensemble cast, Stone takes the de facto lead – Eugenia "Skeeter" Phelan, a would-be journalist living in Jackson, Mississippi, during the Civil Rights movement in the 1960s. Deciding to pen a book about "the help" – the black maids who cook and clean for their white employers – Skeeter's book causes a storm in their segregated community, where women such as the awful Hilly Holbrook (Bryce Dallas Howard) campaign for their domestics to use separate bathrooms.

Like the book, which becomes a word-of-mouth hit, the film itself has gradually grown in popularity – though Stone is unsure why it touched a nerve. "I think it might be because our culture has become so wild about escapism. So many movies are about the location it's taking place in, or the stunts and the explosions, which I'm all fine with; I love escapism as much as the next person. But I think people also like a good old-fashioned story. And this has so much within it."

Part of her preparation was to watch the six-part documentary series Eyes on the Prize. "It was incredible," she drawls. "It was so enlightening and horrifying reading about the Jim Crow [racial segregation] laws, which I had no idea existed, and realising just how separate everything was. It was all new to me – and thank God I know it now. I think Eyes on the Prize should be required viewing in schools, because just to appreciate how far we've come has changed my whole life. "

James Mottram

'The Help' opens on 26 October