There is very little contrast in my model. The model frankly looks like one big blob, despite its having a complex shape. I can really only see its silhouette shape. The only details that I can see inside of the shape are created by the spot light, which is always very faint no matter how I tweak it.
What is the key to getting the shape of an object to appear clearly and to get some contrast?
Did you create normals for your triangles and pass those in? You never mentioned those, and surface normals are required before directional lighting works (A normal is a ray that is perpendicular to each surface, usually from the center of the surface.
I don't have my OpenGL references handy, but I remember the 3 kinds of lighting as directional, ambient, and specular, where ambient is global, and directional and diffuse depend on the lighting direction and the surface normals.
I would suggest starting with 1 light source first and figuring that out, then adding more lights once you get your single light working correctly.
The problem was, although I was creating normals and providing them with glNormalArray, I had not enabled GL_NORMALIZE so they weren't being used. I had been under the impression that GL_NORMALIZE automatically created normals, which is the opposite of what I wanted.