I was actually going to write a simple tutorial to help you step by step but I think you already know how to UV map it’s just some of your faces are blank. When I went through the process step by step, I actually managed to get 2 cases where my faces were all UV mapped and my normals were fine but some were either black or blank.
If you have a shape where any of the faces are hidden from all light sources, then they will go pitch black in the render. If you select the shadeless button in the materials panel, you should see all the faces. Normally you want shading so just make sure the faces you want to see aren’t completely hidden from every light source.
These faces were visible in the 3D view, though. So, it may be that some of your UVs have collapsed. If you somehow shrunk some of your UVs down to a single point or a line by accident, then the faces are blank in every view.
I think the best thing to do is to select one of the faces that are blank in UV face select mode and check what the corresponding UVs are like in the UV editor. Just make sure they are actually above an image of some sort.
If all that is fine, check that you have mapped all of your materials to UV instead of orco. You have to do it for every model in your scene.
If none of that helps, dump your .blend file onto geocities.com. If you have a yahoo account, it is already set up. You just upload your file via web browser. Zip it up first though.