Writing is a kind of creative thinking activity. The teaching of three-part argumentative writing is crucial in college English instruction. Many English majors that fail to write well lack sufficient input of English argumentative reading materials, use Chinese thinking and structure to express their ideas, and lack frequent and sufficient writing practice in English. This paper reviews the application of scaffolding theory and schema theory in writing, and proposes a series of training strategies of blank-filling writing, guided writing, controlled writing, and free writing. Through this series of training that is based on the process approach, the product approach as well as the genre approach, students can gain better writing skills. They can learn how to plan before writing and improve their abilities to write argumentative essays in English effectively.