Novice Lightmapping/baking problems?

I attempted to bake a lightmap into my scene, and made sure that meshes/terrain were static, "generate lightmap UV" was ticked, and a directional light source was established. Keep in mind I am pretty much a pure novice. Anyway, this is what resulted:

http://imageshack.us/g/191/screencap1f.jpg/

The shadows got spotty, and many of the surfaces remained flat and indistinguishable from each other. In an attempt to fix it, I cranked resolution, contrast, and ambient occlusion up. Any ideas on how to fix this, and how to get my scene as photorealistic as possible?

Note that the house model was imported from Sketchup. I am also using the free version of Unity.