"Always design a thing by considering it in its next larger context - a chair in a room, a room in a house, a house in an environment, an environment in a city plan." - Eliel Saarinen
Writing formal analysis means not only to describe a work of art but also to understand what the artists wanted to convey to viewers and what methods they used to do so. If you analyze paintings you have to pay attention to such elements as color, space, scale, and composition. You also want to discuss palette, linearity, balance, flatness or spatial depth, brushstroke, among many other things. When discussing a sculpture, you might want to talk about view point, materials, surfaces, volume, color, orientation, shapes and size. With a work of product design or decorative art, you can talk about its function, materials, complexity of forms, color and texture, as well as techniques and processes used to manufacture a particular piece. While talking about interiors pay attention to proportions and color, materials and finishes, scale and functions, acoustics and lighting, furnishing and textiles. In digital art you can discuss elements typical for traditional media and also the technology that has been used or effects made possible by a specific technology.
Although you are analyzing the formal "language" of a work or a group of works of art, you should consider them in the larger context of specific time and culture, particular political, religious or social milieu, location and use. Comparing to other works of the same style or similar subjects can be also helpful.
Read more about formal analysis on the Getty website.
Always remember to acknowledge all used resources. For more information on citing, review "Citing Images in Architecture, Art & Design", which contains examples of citing materials a well as links to online resources for citation management.
Following books contain some tips for writing your papers: