Sure is a broad. Question. At 23, you are leaving the pediatric cancer age, and few of these are environmentally or habit related, but the simple answers of avoiding tobacco, eating right and exercise work ubiquitously. Many are focusing on issues of "survivorship." going through cancer causes "ptsd"-like trauma and groups grouped by disease help provide common experience support.
DEPENDS. Depends upon type of cancer. Follow up with your pcp/oncologist for early detection of recurrence. Avoid circumstances that caused initial cancer. Avoid smoking alcohol good nutrition exercise avoiding saturated fats will help.