There is nothing more aggravating when the louvers in your shutter panel do not maintain the position you leave them in.
Upon closer examination or your shutter panel, you will notice a stick that runs down the center of the panel that is attached to all the louvers. This stick is called a tilt rod. All things being equal, the weight of this tilt rod and the force of gravity have a tendency to drag the louvers down and in a closed position.
To counteract this tendency, manufacturers will design some means of increasing the tension within the panel. The two most prevalent ways of doing this is by a tension screw assembly or a tension springs assembly.

If your panel has tension screws, they will be recessed into the shutter stile on the same edge that the hinges are attached to. This screw, instead of a shutter pin, is used to support the louver within the panel. When the screw is tightened, it draws the louver into the stile resulting in increased tension. Since every louver is attached to the tilt rod, tension is transferred to all the louvers. Over time, this tension screw has a tendency to back off requiring periodic re-tightening of the screw. If you find that the screw just turns and never tightens, it is likely that it has been over-tightened at some point, and is now stripped. Removing the screw and installing a longer screw should remedy this situation. By using a longer tension screw, you are working with new wood in the louver and giving the screw something to bite into. You will notice that these tension screws are simply regular drywall screws found at most general hardware stores.
If your panel does not have tension screws, it likely contains tension springs. These springs are not visible because they are located in the Stile behind one or more louver pins. The springs will only be found on one of the Stiles of a shutter panel. The spring pushes against the louver pin and louver. Tension is increased by driving the louver into the opposite Stile. Tension Springs are generally found on the second louver from the top and bottom. Poorly constructed shutter panels that contain tension springs can lose their tension. When this happens, tension can be increased by installing additional tension springs using a shutter tension kit. The number of additional tension springs will be predicated on the size of the panel, total number of louvers, and size of the louvers. Installing tension springs with a Shutter Medic® Tension Kit is a simple task that can be performed by the average homeowner as demonstrated in the video below.