Ever wondered how to capture the perfect candid moment of your friends? Let Keegan Allen teach you how it's done.

An avid photographer since childhood, the "Pretty Little Liars" star is showcasing his work in his new photo journal, "life.love.beauty." Speaking to MTV News, Allen gave us a few helpful tips for taking the perfect candid and revealed how one of his favorite candid shots of his pretty little co-star Shay Mitchell came together.

"One of my favorite photos in the book is of Shay Mitchell at the beach -- it's a two-page spread -- and that was a candid shot," said Allen. "It looks totally staged!" Clearly, Mitchell is always camera-ready. "She is," Allen said. "And she does that mirror-face [impersonates Mitchell]. I can't do it because I don't have long hair, and I'm not Shay."

"Always keeping a camera with you is important," Allen added. "Even if it's an iPhone."

As for which of his "Pretty Little Liars" co-stars is his biggest muse, Allen said it's "whoever wants to pose for the photo at the time." Okay, we understand Allen is trying to stay impartial, but it's obviously Troian Bellisario. Right?! (#SpobyFeels)

"life.love.beauty" is on bookshelves now.