The first step for me is to decide what parts of the model can be totally seperate and what must stay together. A stereo system with say 5 speakers could be 6 individual props. If though the stereo has a turntable for records, an arm to play the record, volume and tone controls and a slide out cd tray then you want 1 item with a number of moving parts, and thats what a figure is for.

I use lightwave so my workflow for machinery is roughly.

1. model the thing

2. assign surfaces (material zones)

3. assign parts (remodel as required, unweld as required)

4. Save as obj

5. uv map obj

6. use Phibuilder to set hierarchy

7. create figure in POser

8. edit pivot points (parts centers) using joint editor

9. assign materials

8a create any image maps needed, ditto bump maps, transparency maps etc

9 unhide trans dials if needed

10. change dial names to describe correctly open/close, turn

11 hide unused dials

12 save figure

13 render new thumbnail 91 x 91