There's a bewildering variety of methods and systems and traditions when it comes to how carmakers name their cars. Luckily, I took some expired medication that lets me know which ways are the best. Even more lucky is that I'm now going to share this wisdom with you, because you know I love you best. Here we go.
1. Animal names
2. TIE: Mythology-based names or human names (Nissan Cedric/Silvia, GMC Jimmy, etc)
3. Numerical names based on engine displacement
4. Location names
5. Names based on a common theme throughout the company (i.e. Volkswagen's wind-based naming or Lotus' names that start with E or Rolls-Royces naming cars after spirits and ghosts and spooks)
6. One or two letters, one or two numbers
7. Made-up names, usually weird
8. Complicated alphanumeric names that fit some complex but consistent system
9. Complicated alphanumeric names that don't seem to fit any system, no matter how Byzantine or absurd
There you go. Hope that helps.
BONUS FUN: Try making car names from a noun+animal! It's fun! Fiat Ironemu! Daewoo Firegoose! Maybach Thunderlamprey!