Never buy a car that does not have MAJOR devices to prevent you from
leaving your lights on and locking yourself out. I used to leave my
headlights on EVERY time I drove with them on during the day (during rain,
etc.). Now I have a car that dings politely if I turn the ignition off
while the lights are on, and I thank my car out loud each time it does so.
Corollary to this rule:
If your car lacks these devices, NEVER go anywhere without a
set of jumper cables and always keep a spare key on the
undercarriage. (And, if you use the key, put it back IMMEDIATLY!)