Encourage students to try some debugging off-screen. A common strategy in debugging is to read through each step in the code and trace on paper what the result would be. For example, when working with sprites in Scratch, you can have one student read the code while another acts as the sprite by drawing or moving around the classroom.
Example: "Read the code aloud and pretend to be the cat!"
See this and related tips as a Tip Sheet: http://csteachingtips.org/tips-for-teaching-scratch