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. Before I start the modeling I will draw a cage from the referance images using CV curves. The curves will work great as snapping points and referance later on.

3. 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. 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. Only make half of the car because you can easely mirror the geometry when you are finnished.

5. The body almost finnished.

6. I found a great reference for the wheel and started making the tracks by splitting a polyplane. I then duplicated the object a hundred times and combined and merged the objects. I used the bend deformer to bend it around. In the center of the wheel I modelled only 1/7 part of it and duplicated it around.

7. The final image is rendered with mental ray using HDRI and blured reflections.

8. Car with wheels.

9. Interior modelled with mostly basic extruding.

10. Interior with textures and shading.

11. Render showing of the car with al the details. You can see more images of the final car in my portfoli section.