Hi Fran,
Try using Wings to set up the model as much as you can first. I use the materials in Wings to determine the shading domains in Carrara. The only thing you really need to do is plan your model as much as possible - setting your Wings materials up as boxes, cylinders or flat planes to make life easier when UV mapping. And use different colours for each material - makes life much easier as well. Have you used Wings UV mapping functions before? I use UV Mapper Pro so I won't be much help with Wings or Carrara UV mapping, but it ought to be similar.

When importing into Carrara do the following:

• Import .obj options: Select Vertex Primitives and under Grouping select Create only one object (unless you want each material as a detachable object).
• Select your object and go to the Model room.
• In there you'll see the materials are marked by blue outlines and you'll be able to select them via the Selection menu Select By/Shading Domain...
• You'll need to do the UV mapping to get the textures looking right, otherwise you'll usually get odd overlapping bits on your textures if you leave them as they are.
• In the Texture room you'll find the shading domains on the right of the screen, double click each one to edit them.