Inspect for wind, snow, or ice damage. Check to see that the roof shingles are secure, tightly fastened and in good condition. If any of the shingles are loose, repair with asphalt roofing cement. If they are damaged or missing, replacement will be necessary and may require professional help.
Inspect the flashing around the chimney, plumbing vent stacks, electrical masts, and in valleys where roofing sections meet. Repair or re-flash if the flashing has deteriorated.