Now the illuminating face of an object with a spotlight material type is determined by the face with the most number of vertices. If there is more than one face with the most number of vertices the lowest of these faces is used. For a block every face has four vertices, so the lowest face of the block will be lit. For a cylinder the two endcaps have the most vertices, by default 16, and each face of the walls of the cylinder has only four vertices.
To make a spotlight shine upwards start with a cylinder. Use the circle tool to draw a circular polyline. With the arrow tool space-jump to a handle of the circle and while holding the option-key drag the mouse upwards to extrude the circle into a cylinder.
If you asssign this object a spotlight material, move it above ground, and view Lights and Textures you should see the lower of the two endcaps lighting up.
Return to the standard DesignWorkshop window. Select the cylinder and then choose the trim tool from the tool pallete. You need to trim the cylinder so that the trim line passes through the lower endcap of the cylinder and comes out the side of the cylinder. Now delete the little corner you trimmed off.
The cylinder's lower end cap is now made up of two faces, each with about half as many vertices as the upper end cap. So now the light will come out of the upper end cap and shine upwards. You can rotate this cylinder in any direction you please and the light will always come out of the untrimmed endcap.