Here is a small "step by step"- tutorial, showing how I usually make these car drawings.
This perspective is a quite difficult one compared with the earlier ones I have posted here, so the initial scetch is quite messy. Fortunately things have a tendency to turn brighter when starting working with volumes and reflections. The way of work is quite straight forward from 1-3. The development between 3 and 4 is very iterative and again,...messy. I´ll try making a more complete tutorial next time ;-)