Cinema Retro columnist Dean Brierly has a great article on his blog: classic quotes from legendary actors and supporting actors. Here's a good example from Bela Lugosi:
(On Dracula) “In playing the picture I found that there was a great deal that I had to unlearn. In the theater I was playing not only to those spectators in the front row but also to those in the last row of the gallery, and there was some exaggeration in everything I did, not only in the tonal pitch of my voice but in the changes of facial expression which accompanied various lines or situations, as was necessary. But for the screen, in which the actor’s distance from every member of the audience is equal only to his distance from the lens of the camera, I have found that a great deal of repression was absolutely necessary.â€(1930 Hollywood Filmograph interview)
Click here to indulge in many more