Kirsten Dunst knows how to say no without ​L​osing ​F​riends and ​A​lienating ​P​eople.

The actress demurred when director Sofia Coppola suggested that she shed a few pounds for her upcoming role in “Beguiled,” a version of the Thomas P. Cullinan novel that also stars Colin Farrell and Nicole Kidman. “It’s so much harder when you’re 35 and hate working out,” Dunst told Variety magazine, adding that Coppola backed off from the request without pressuring her further.

The “Lost in Translation” filmmaker and Dunst are famously tight: they first met in 1998, when the director was 27 years old and the actress just 16. But even if you haven’t known your boss for 20 years, management experts say that there are smart ways to decline requests that could actually advance your career.

Firstly, don’t equivocate. “If you feel like you have to say no, make it your first response,” says executive coach Debra Benton, co-author of “The Leadership Mind Switch.” The reason: it makes you look decisive, which is a quality many employers respect. “Don’t say ‘let me think about it’ or even worse, agree and then say no,” she says.

Having an alternative even when you decline to do something is also crucial. “There are many non-adversarial responses that can show your flexibility,” says career coach Roy Cohen. For instance, if you’re asked to stay late to complete a project, he recommends offering to do it from home or coming in early the next day to finish up. In the event you’re busy doing something equally pressing, tell your manager you’re happy to set it aside if your supervisor doesn’t think it’s really that important. “Always do it by email so you can set aside” a paper trail, suggests the author of “The Wall Street Professional’s Survival Guide.”

Indeed, celebrities who are often bombarded with requests have perfected the art of demurring gracefully.  “Harry Potter” actress Emma Watson recently told Vanity Fair that she declines all fan selfie requests for security reasons, though she’s happy to offer autographs and answer any questions they may have about the boy wizard. Benton recalls witnessing an incident in a New York hotel elevator in which Britney Spears’ bodyguard turned down a request from a father and daughter duo who wanted to snap a photo with her. Instead, the bodyguard took down their address so that the pop star could send them a signed photo.

Still, experts acknowledge that having the courage to say no often isn’t easy. That’s why it’s important for each individual to know their boundaries, as well as when those walls can be flexed. “Your boss and colleagues are going to see you as a patsy if you don’t say no when it’s appropriate,” says Cohen. Though he adds that turning down things too often could harm your shot at a pay raise or promotion. “At the end of the day, if you’re always in a situation where you have to say no, you may be in the wrong organization.”

For those still inclined to refuse, polite disagreement is happily a skill that can be finessed and trained. Benton even suggests occasionally saying no to requests you don’t mind acquiescing to, just for practice. “You’ve got to develop that muscle,” she says. “People talk about work-life balance. Well, that’s all about saying no.”