A common approach is shown in the figure below; A diode can be put in series with the circuit. That way, even if the input is reversed, there will be no current path and device will not be damaged. However, the disadvantage of this approach is that there will be a voltage drop of around 0.2 V on the diode during normal operation
Another method is based on the use of fuse+diode as shown in the figure below. With this method, there will not be any voltage drop of the diode during normal operation. When there is a reverse connection, the diode will be conducting, and the fuse will be blown to protect the circuit and the device. The disadvantage is that you may need to replace the blown fuse.