The four steps to art criticism are: to describe what you see, analyze the elements the artist has used, interpret what the artist is trying to say, and evaluate its importance. This kind of analysis is done in an organised approach.
Aesthetics is a study of art. An art critic should describe the subject matter with a personal approach. He should analyze the mood of the art as a result of the elements used by the artist. Then, he has to interpret by suggesting what the artist is trying to say using the previous stages that have already been concluded. Finally, he should add his own judgement on the value of the art.