This is the second time my car has died on me in the one month that I have owned it. Everything has been running fine until I parked it for 30minutes and then it wouldnt start.
No cranking No trying to turn over No noise turning the key and the lights are ok
Most likely a dead battery. Start by getting a jump start.
Do the lights on the dashboard turn on? If there is no sound when you turn the key, but the lights and accessories work, it could be the stater relay or starter solenoid.
However if there is no sound at all, not even a click, it's probably your battery.
if the lights are on and remain on when trying to crank but the problem is that the starter does not even attempt to engage then this points to a problem with either the ignition switch or the exciter cable, this is the narrow gauge cable attached to the starter which, when made live, engages the solenoid to begin the cranking process.
I had a very similar problem to what you describe and was able to bump start the car (it was a manual). I traced the issue to a frayed exciter cable just above the starter motor itself.
If the lights are OK, then I would check a few more things.
Check to see that other accessories work ok, like the radio and the fan.
If you can run the fan, and the lights OK, then likely the battery, and the battery connections are not a problem.
Do the engine cluster lights check OK, which would mean that the oil and check engine light come on with the ignition turning on?
If yes, then your ECU (computer) is likely working OK.
If everything works to this point, I would be suspicious of either the solenoid for the starter motor, or possibly the ignition switch. Usually there is a fusable link or a large fuse for the starter solenoid. With someone listening under the hood, activate the starter, and have them listen for a click. If no click, the ignition to starter solenoid is likely the issue. There could be a failed starter, but they usually do not fail suddenly.
The make/model/engine for your car would help better guide you to a starting solution.
I'm posting for future people that have this issue. So I had this issue today with my standard transmission car and none of the answers that I found online was actually the issue. It ended up being an issue with the clutch safety switch.
Before you go out and spend a lot of money follow this checklist.
Check the battery
a. Are the headlights coming on and are they bright? If they aren't it could be a battery issue.
Is it a manual transmission?
a. If so check the clutch safety switch. This is found at the top of the clutch pedal. 
That black peg has to be pushed in for the car to start. In my case at the top of my clutch pedal there was a rubber piece that was in the metal that pushed it. However, it go destroyed and broke off, that's why my car wasn't starting.
If you have a manual car a way to get around this (temporarily) is to push the car until it's going 4-5 mph. Get in and put the car in first and the turn the key and release the clutch the car should start up. This can get you out of a bind really quick.
Its your starter. I literally am going through this same thing as we speak. The car lot I bought my kia rio from came and towed it. All my interior lights worked , radio , a/c , turn signals etc EXCEPT for my headlights . Starters can die a silent death with no indications unfortunately.
This happened to me and after chasing all the usual culprits it turned out to be something unusual... Ground cable for the starter had fallen off the car. Shop that replaced my starter did not know a cable should be there (because they didn't have to remove one)!
