First make sure everything else is getting power and operating okay, and that it is only the LCD display that is non-functional.
If you get no video signal or power at all, even at boot time, you probably have a dislodged ribbon cabling or power connection. Usually when LCD monitors go bad they show colour banding or all white, etc., but usually continue getting power.
As a last resort, try disassembling the lower case (with the power disconnected and the battery out of course) to expose the LCD monitor mounts, and then following the wiring from the screen into the laptop and check for anything loose or disconnected. You could also have a loose ribbon cable going into the LCD array, which will require disassembling the LCD cowling and mounts.
If you are handy and comfortable with electrics and find nothing loose, put the battery in and test the power line going to the LCD backlight, which should be getting above 7V (I think). Below that and you either have a bad video controller or bad wiring/solder joints somewhere. Otherwise, if the unit has been dropped or had a hard life generally, it could also be the connections between the LCD connector bus on the monitor array and the array itself. As a last resort, try unplugging and reconnecting all ribbon and connector cables, cleaning the exposed brass coloured runners lightly with rubbing acohol or even a pencil eraser.