Normals

Hi! I''ve been trying to get lights to work, but whenever I add normals, it looks as if the rectangle I''m testing it with gets smaller(and keeps changing size proportionally to the window. The size is correct when I don''t try adding normals, so that should be ok I guess. Well, I''ve tried setting the normals x and y values to 0, and z to -1 (1 as well). I''ve also tried putting the same coordinates as the vertices have, and adding/decreasing the z value. I''ve tried a few different combinations as well, but it doesn''t really work. Could anyone give me a tip or perhaps tell me about a good place where I could read about using normals?