Sagging. Remove loose screws from hinges and fill holes with plastic wood. Then reset screws and draw all screws up tight.
Rotting along top edge. Dig out soft wood and saturate the entire top of the shutter with pentachloro-phenol wood preservative. When this has dried, fill holes with plastic wood. To protect against further rotting, tack a strip of aluminum flashing over top of shutter.
Adjustable louver broken. Try to glue pieces together with Elmer's waterproof glue and tack a strip of aluminum to the back of the louver for extra reinforcement.
If louver is beyond repair, remove it and make a new one. After you have shaped the wood pivots on the ends, cut a U-shaped slot about 1" long and the width of the pivot into the louver at the end of one of the pivots. With this pivot removed, you can now fit the louver into the frame. Then coat the sawed-out end of the removed pivot with Elmer's waterproof glue; insert the pivot end in the frame; slide the sawed-out end into the slot in the louver and bind it in place with adhesive tape until glue dries. Final step is to secure the louver, at the middle, to the adjusting arm with small staples.