1.Always start your car project with finding good referance images.
http://www.the-blueprints.com/ is a goog place to start. Place your images either as imageplanes or as a texture on polyplanes.

2. Start the modeling by placenig a polycylinder around the wheels, delete the caps and start extruding the edge to make the side of the car.

3. It's recommended that you let the geometry go in circles around holes in the mesh (place the faces in a circle where every face is rotated against the next), like around the frontlights on this image.

4. Let the edgeflow in your mesh flow like the lines in the car. I recommend making the doors as seperate objects so they can be opened later on.

5. I use as few polys as possible to keep the mesh clean.

6. The body finnished.

7. The wheels are made with a cylinder where all the facers are extrudet separately (see my tutorial "Modelling a tire with polygons in Maya" for more info).

8. Just a test rendering of the wheels.

9. Start adding details. Most of the objects are just boxes og cylinders that are extrudet and shaped.

10. Interior modelled with mostly basic extruding.

11. Interior with textures and shading.

12. To get a nice studio render of you car i recommend using a lot of white and black planes around the car to get nice reflections and a shiny render.

13. Studio render of the final model.

14. Studio render of the final model.

15. The final image is rendered with mental ray using HDRI image as both lighting and background. You can see highres version of the image in my portfolio section.