As an old woman in search of the love she abandoned in Italy 50 years before, Vanessa Redgrave puts on an acting clinic in “Letters to Juliet.” If only the star of this romantic comedy, Amanda “Mamma Mia!” Seyfried, had taken notes.

Lovely Amanda – playing a New Yorker fact-checker who stumbles across a weathered “letter to Juliet” left at the house that tradition says was home to Shakespeare’s legendary heroine – does little to animate her character in a movie built around her efforts to bring two long-parted lovers back together.

But Redgrave, the Oscar-winning pro, keeps trying to show her how it’s done. Give the camera something to look at every time it’s on you – an expression, some little bit of business. When her character, Claire, folds Sophie (Seyfried) in a motherly embrace, Redgrave twirls Seyfried’s hair as if she were forgetting herself and thinking this was her own daughter.

You relish magical moments like that, because “Juliet,” directed by the chap who inflicted “Bride Wars” upon humanity, is mostly blown opportunities. It has humor and a touch of charm, but plainly needed more love, more passion, more Shakespeare.

Seyfried’s Sophie is in fair Verona on a “pre-honeymoon” with her workaholic chef fiance (Gael Garcia Bernal, adorably manic). Left on her own to sight-see, she visits Juliet’s house, sees the “advice to the lovelorn” letters weepy women leave there, and follows those notes as they’re collected by the “Secretaries of Juliet.” They take the letters?

“Si,” the ladies say. “How else can we give them the answers?”

Sophie stumbles across a 50-year-old plea, answers it, and this lovely British widow (Redgrave) shows up, much to the annoyance of her cranky grandson. Christopher Egan plays Charlie, who reluctantly drives granny Claire and Sophie around as they search for Lorenzo, that love who got away. Egan looks a little like Heath Ledger, without his charisma.

It’s a movie of blandly pretty “establishing shots,” Seyfried walking her lovely self across this piazza or that vineyard. Director Gary Winick wrings a few laughs out of the search — “Lorenzos” both handsome and decrepit, or sadly, no longer with us. A bit of stunt-casting makes the search pay off, warmly. But the real courtship here, between the spoken-for Sophie and the doesn’t-believe-in-love Charlie, fizzles.

Still, “Letters to Juliet” has the smell of a romance-novel hit (like Seyfried’s “Dear John”). That’s a shame, because until Seyfried starts taking notes from the Redgraves and Streeps she is honored to work with, she is never going to be anything more than fair-faced set dressing. And as the Bard warned her, “every fair from fair sometimes declines.”