Help with making a script?

I want to make an xray script, and when I press a key, I can see everyone through walls. How would I accomplish seeing people through walls? I can do the rest, I just don't know where to start.

You would probably want to have BillBoard Guis constrained to that player if they have the xRay vision glasses on. This could probably be achieved through a local script using the Local Camera, although I am not too sure about how you would do that.