1. Check the battery. If the battery is dead or weak, it won't be able to provide enough power to start the engine. Try jump-starting the car to see if that solves the problem.
2. Check the fuel. Make sure there's enough fuel in the tank and that the fuel line is clear.
3. Check the spark plugs. If the spark plugs are worn or dirty, they won't be able to create a spark to ignite the fuel. Try replacing the spark plugs to see if that solves the problem.
4. Check the ignition switch. If the ignition switch is faulty, it won't be able to send power to the starter motor. Try turning the key in the ignition to see if that solves the problem.
5. Check the starter motor. If the starter motor is faulty, it won't be able to turn the engine over. Try tapping the starter motor with a hammer to see if that solves the problem.
If none of these solutions work, you may need to take your car to a mechanic for further diagnosis.