Step 3: the baked model is renamed (for clarity in the Unity3D editor) and the model saved. In the background, Unity3D will let Cinema4D generate a proper FBX file for import and load all. Hide the non-baked mesh and only display the baked one. Switch to a Lightmapped Diffuse material and point to the right texture maps for the material.
Beware, there are some minor issues:
* be sure to hide the original mesh in Unity3D
* if you include illumination into the baking process in Cinema4D, be sure to copy the texture map also in the Diffuse channel, to have proper UV-coordinates for the mesh in Unity. Otherwise, you end up with a black mesh.
* Inside Unity3D, hide what you don't need and make sure the correct baked textures are used by the materials.