Personally I start with a cube, its all down to preference at the end of the day, as Mike uses cylinders, I believe Kurt uses a nurbs sphere now and then for blocking then converts later.

Yeah always add the geometry as you go, start as low as possible and push the shapes as far as you can before adding more to it. Check the topology thread in the WiP section, theres plenty of wires there to muse over.

Cheers
Jay