The Formal Analysis of a painting is the physical look of the painting. There are many different properties (ie: line, color, size, material, composition, etc.)
Not only do you have to discuss what you see, but also figure out what the image is portraying and analyzing the meaning. By looking at the physical features and focusing on exactly the way they are placed within a piece of art might give you insight of why the artist placed it there. Most of the placings are intentional and you will turn up understanding the artists mindset by just looking at the physicality of the piece.
I agree with your comment about intentional placings. I too spoke about how artists may use certain techniques, colors, or place certain items in certain places in order to convey how they truly feel, without having to say anything. Their emotions are left in their art.