Although in art an idea which visualizes a certain concept is generally such an essential part as it would be decisive to the success or failure of an art work in reality various difficulties are involved in idea making. Thus, directions for the idea making for visualization works are suggested in this paper. This paper classifies several cases of expression skills among non-abstracts showing the contents which visualize abstract concepts in western art after Renaissance when freedom of individual artistic expression and personal characteristics initiated. Also, this paper selects and introduces art works in which expression skills can be obviously explained. The expression skills are divided into symbolizing, allegory, specific pattern, non-abstract skills of surrealism, metaphysical distortion of logic and situation fixing, and specific examples on how the abstract concepts are formed and delivered are described. This is a case study done for the purpose of supplying help for the idea making in the applied art field which is lack of this kind of study.