If there is complete display failure, first of all check the status of the power. If you were able to hear the fan of your laptop and now it isn’t, that means it’s a main board or power failure, not a video failure.
Another common practice in laptop computer repair is to connect a normal computer monitor with a standard VGA connector, if your laptop does not light up the external monitor means either the internal video adapter or the motherboard has failed. In case the external monitor is working then your laptop video subsystem has a problem and need to investigate further.
If there is a display problem in your laptop computer and the number of dead spots or columns or whole row increases slowly on the screen, it indicates that the assembly of actual LCD is bad. In the same way, if the screen flickers it is probably the failure of backlight or inverter.