I'd start by checking the fuses, and if none are blown, then a ground wire might have come loose. If that's the case, you might want to have it checked by a competent mechanic. Or you can check it yourself if you're capable.
It depends what is wrong with them.
Check the fuses.
It would depend on what is wrong with the headlights.
mine does the same thing. no clue!
The ground ciruit for the headlights is by way of the headlight switch , the lights always have power
This may be caused by the ignition switch.
You will need to be more specific. What exactly is wrong? Are they power windows?
Sounds like some one hooked it up wrong.
the battery is flat
you have bought a general motors car
Recheck fuse #9. This one has a tendency to go out more frequently than others and is associated with all of the mechanisms you noted.
my headlights work but my taillights and dash light dont work whats wrong