Does anyone know a tutorial on how to model a car?
I suggest to start with existing free models, e. g.
http://dmi.chez-alice.fr/models1.html
Import them as .lwo, then play some time adjusting the size, rotation and materials.
What you soon recognize, is just the need of good skills of basic modelling: understanding the viewport, mesh tools, grouping methods, and that kind of things.
Get a blueprint of your favourite car, e.g.
http://www.the-blueprints.com/index.php?blueprints/
Adjust the image with Gimp, make three fotos, same scale, midpoints exactly, then use each as an background image, and just go putting the first vertices on their places, you soon see what you need and what you dont. Keep your workspace logical, top view window at north-west, front view at SW and side view at SE, so they correspond to numpad key locations Num7, Num1, Num3 at your keyboard. Try to use mirroring as much as possible, only model the other half of your car, it saves the half of modelling time. Learn to use it effective, and try to find the logic behind global and local coordinates.
Does anyone know a tutorial for modeling a car?
There’s one in the BlenderArt car modeling issue (#8 I believe). www.blenderart.org.
Also, you could try http://www.3dm3.com/tutorials/car3/, or http://www.3dm3.com/tutorials/maya/350z/. Neither are for blender but the techniques covered should be similar if not the same.