Typical flow of a statement of purpose:
1) Begin by introducing yourself to the reader and provide some details about your personal background as it relates to the field of study
2) Then discuss your academic experiences as they relate to your field- include both academic activities as well as extra curricular activities
3) Then discuss your research experiences or if none, talk about your research related courses and how they prepared you for research
4) Then make the connection between these experiences and your field of study- it is good to mention a major idea in the field of study- it shows that you are knowledgeable and think about the field.
5) Mention any special aspects of your application (grades, GRE scores, publication)
6) Move on to what you expect from the program and your career goals
7) Mention why program is a good match with career goals
8) You can standardize your statement but should tailor the last paragraph specifically for each program that you apply to…reviewers will note this