Drawing car is fun (I'm obsessed with anything that is old and has 4 wheels). To get them right I almost always use refrence photos. I want them to be regocnizeable, so it is possible to see what make and model they are. I know this probably doesn't matter to 99% of the readers but it matters to me.
The process of drawing them is simply to decide what kind of car I need, find the right photo, and then draw directly from the photo. And remember to make it fit properly into the drawings perspective. This is VERY important. At least if you want a certain sense of realism.
If the car is supposed to have any other color than a shiny black, it usually ends up as a clean lineart drawing. If it will be black and shiny I usually fill in everything when I'm inking and leave some white space as reflections. Shiny black is probably the most reflective car finish (at least it is in the real world). According to the guy who owns the local automotive paintshop where I live it is the hardest color to pull off.
There is a few cars here. And also in the following chapters. As I'm interested in classic cars, everything I draw that has wheels will be at least 30 years old. Newer cars doesn't interest me at all. They may not be considered normal today but they used to be.