Extreme measures have been known to be taken, of course. During the shooting of a scene in At Close Range, Sean Penn went off and loudly asked the prop master to give him a different pistol, and so returned and pointed a new, strange gun at Christopher Walken who then later said that this did the trick for bringing out his genuine fear. In the scene at the end of The Exorcist, where the priest gives Father Karras his last rites, just prior to the camera roll that priest was slapped in the face by director William Friedkin.
Ready for my close up.
Now, let me be clear, I'm not suggesting it be open season on assaulting your talent, and any drastic measures you take should be matched by your absolute certainty that this performer is possessed of the reckless spirit for art being long and life short and all that (especially if you need them to stick around and shoot more footage afterward), but there are all manner of means to shake things up.
I was shooting a scene for my movie, "On The Inside," with the amazing actor Dash Mihok; and I felt it was going flat, and so I leaned over and told Nick Stahl, who was delivering the off camera lines, to mix it up and say something crazy instead of his normal line. When the scene started, instead of saying his line as written: "You're the salt of the earth." Nick said instead: "You're the kitty-cat's ass." Dash had this moments jolt, and then there came over him a whole new freshness, a kind if "Oh, it's like that, is it?" and he jumped into the scene with verve and sharpness and that's the take that's in the movie.
Shoreh Ahgdashloo.
Another technique you can use, a good one even for occasions when you have lots of time and things are going well, is to tell your actor to say a short phrase that represents the basic thrust of what you'd like them to express at that moment. I call this expression a "gist phrase." Something short with bite such as: "This is over." or "I'm here for you." or "Don't be so serious." You can let them do their own version of the gist phrase, using language of their own choosing, but have them say it several times until you feel them connect and committing to the action, and then tell them to say the lines of the text with that exact reading/intention.
Of course, there are no pat solutions when it comes to producing art. That's why it's art. That's why it's great. Everybody runs into times when it seems to flow and others when the magic seems nowhere to be found. The important thing is to, in some way, love it all; because that's the nature of the beast. If it was subject to your certain command, it really wouldn't be that much fun. And, hey, it's always possible the magic is just around the corner.
D.W. Brown is the head instructor at what’s commonly considered Los Angeles’ premiere acting school, The Joanne Baron/DW Brown Studio in Santa Monica. D.W. has written a definitive book on acting, You Can Act published by Michael Wiese Productions (“Shot By Shot,” “The Writer’s Journey”), and is in post production on the feature film On The Inside, that he wrote and directed, starring Nick Stahl, Olivia Wilde and Shoreh Ahgdashloo.