Step 2: Modeling the Front of the 500
The front part contains the holes for the headlights and for beginners it might be more difficult.
Model the profile of the front part by extruding and moving vertices. Then, in Edit mode (front view), place the 3D cursor in the center of the headlight and add a circle (6 vertices). Connect the vertices with the front part of the structure using the Fill command (F). It will be better to work only with quads, especially when the Subsurface modifier in enabled.
Step 3: Modeling Wheels and Tires
The tires and wheels of this car model are very simple to model. Add a circle with 16 vertices, extrude the vertices and model the first the central part (add the extra cuts for highlights on the chrome).
With the same procedure, model the outer part of the wheel and the tire. Also, for this part of the model, make sure you've enabled the Mirror modifier and Subsurface.
Step 4: Add Details
Small details make all the difference in a 3D graphic work, and make a model more realistic. Add chrome gaskets around the glass, wipers and bumpers. To add the gaskets, jump into Edit mode and select the vertices of the body close to the glass, then duplicate them (Shift + D).
Separate them (P) into a new object, then convert it to a Curve (Alt + C). In this way we can edit the thickness of the curve using the shape and geometry pane on the right side of Blender windows.