The couple, who had picked out an engagement ring together, were expecting the jewelry to be delivered via FedEx the day before leaving for a getaway together. "Somehow we missed the FedEx truck, and I freaked out," King tells In Style Weddings for its October issue.
"I wanted to go on the vacation engaged, with my ring! So I got in the car, and I stopped two FedEx trucks, saying, 'Do you have my ring?' It was like a scene out of romantic comedy, with me literally chasing down trucks!"
When the package finally arrived, she and Newman decided to take a walk together. After "walking around and around" in a Beverly Hills park, Newman "got down on one knee and proposed," says King.
King, 28, did not have to ponder her response. The couple, who first met in January 2005 on the New Mexico set of Fanboys, directed by Newman, knew their relationship was special from the get-go.
"I really think we meet the right guy when we are ready" King tells the magazine, which hits newsstand Friday.
Within three months of their first official date, the couple had moved in together.
"I didn't have to stop and wonder whether it made sense because it didn't feel like a big choice," says Newman. "Sometimes, things go slow and nowhere. Sometimes they move fast, and it feels like you are picking up where you left off, even though you've never met."
Their wedding, planned for the fall in the same park where they got engaged, will be " intimate and relaxed," says King who plans to wear a Calvin Klein gown.
Up next: Professionally, King will next star in The Pardon, Riding the Pine and Sin City 2. Personally, "I want at least three children," she says.
But for now, "Life is better than how I imagined it. There are things we want when we're younger, but my life of late is better than anything I could have dreamt up."