Discuss tough obstacles you overcame in life. If you couldn't attend college when you were younger due to an unplanned pregnancy but you finally earned your bachelor's degree after several years, talk about how those experiences shaped your beliefs and gave you more motivation to succeed.
Mention your most important accomplishments. If you successfully operated your own non-profit mentoring agency and it has been consistently recognized by your state as an important asset to the improvement in statewide test scores, put this in the personal statement. Or if your magazine articles on children in foster care led to new policies in this area, discuss it.
Talk about your philosophy regarding the social work profession. If you believe that economically disadvantaged families would be better served by faith-based organizations and local community groups rather than the government, discuss why you feel this way. Also mention how you would utilize these groups as a social worker to assist city residents.