In class we have about 2 1/2 hours to paint and I usually ask students to paint on a 12"x 16" canvas, (larger if possible). Breaking away from this standard of size and shape has helped us focus on composition and positive/negative shapes. But where the rectangle has natural directionality and tension because of its height to width ratio - the square has none. The square format suggests strength, firmness, solidity, and - oops - we're on the slippery slope to boredom.
How do we create drama and tension in a shape that has none?
While the stodgy square can not give the sense of wide-screen spectacle - we can give it some small screen drama by the way we direct a viewer's eye through the piece.
Begin with the Rule of Thirds for placement, then work with lines and composition to create excitement. The most dynamic lines in any painting are diagonals. These type of lines can be in the subject matter, edges where values or colors contrast, or even in the brushwork.