Is your battery dead? You might need a new battery.
If the lights are on as normal, maybe there is a problem with the shifter, if automatic. There is some kind of a switch that only lets the car start in Park and maybe Neutral too.
Will the engine turn over?, Is it automatic or standard?, Check battery and selnoid. Remove and clean battery cable connections at battery and all oher connections going to and including the connections to the starter. When testing for current flow past the battery be sure to have key in start position.
turn the headlights on. Now try and start the motor - do the headlight go dim?
If they don't your starter circuit has a problem.
If they do then look to the battery.
There are ways to continue but if you asking these questions your motor might be better of in a shop.
Check bulbs & fuses first. If still a problem you will need to start looking at possible wiring issues
Crank but not start and run, possible. Not to crank, start or run, no. No lights or horn, no.
Check to see if stop lights are working. Shift interlock and stop lights are on (perhaps blown fuse) the same circuit. If stop lights are not working, try turning the key to the 1st position (unlock) and try to shift to neutral to start car and then you can move shift lever.
If the other lights work, look for a bad fuse (I believe the tail lights and dash lights work off the same fuse). As far as the vehicle not wanting to start, it's hard to trouble-shoot without knowing the symptoms (is the starter spinning or not?, etc).
there is a short in the relay for the head lights
Start small. Check your fuses.
fuse
Loose belts
Turn signals not working nor back up lights. However the head lights are working and rear lights are also working
Start with checking the fuses.
First of all is the lights working in the car? (over head lights or any kind of lights) If your not getting anything at all (no lights) then you should check the battery. If the lights are working then I would check your starter. Most of the time if you take the battery somewhere to get checked they will do it for free. So I would start there. Did you try to get a jump to see if that would start it? Hope this helped some.
Have you checked your battery. My battery died on me all of a sudden and I could not start my car.