Give a summary of the guidelines for using sunscreen to prevent overexposure.

Answer:

Choose a broad-spectrum sunscreen with SPF 30 or higher and apply it generously about 15 minutes before going outside. Reapply at least every two hours, and after swimming, sweating, or towel-drying. Use sunscreen along with shade, protective clothing, and a hat; do not rely on sunscreen to stay in the sun longer.