Besides what the other said, take one down and rehang it. Use matchsticks, golf tees, or small dowels glued into old wallowed out screw holes and then redrill them with a small bit when they dry. On the house, longer and bigger diameter screws into studs will help also. You may also want to move each hinge an inch or so and make all new holes. Caulk and paint over the old holes. Fix any loose louvres with some glue and maybe a brad if necessary. The answer you are looking for is easy, the work is something else. Clean, scrape, sand, prime, and paint with 2 coats before putting them back up. Much easier to paint on ground plus you can get both sides. Remember which shutter goes where if you have more than one off. I'll be watching for a post next Sunday night saying you got them all fixed. Good luck.