If your car is smoking from under the hood, here are the steps you can follow to troubleshoot the issue.

#1. Smoking is usually related to engine overheating. Stop driving and turn off the car immediately to avoid catastrophic engine failure.
#2. In some rare cases smoke could be coming from the old car battery, especially if you had many issues with it lately or tried to jump-start it frequently.
#3. Check the temperature gauge to find out if engine temperature is normal or too high.
#4. If necessary, let the car cool down first. Then, carefully open the hood and visually inspect the car for any spilled liquids such as coolant, engine oil, windshield washing fluid, brake fluid, battery acid, etc.
#5. Find the source of leak. Add more coolant if it’s completely gone from the system. You can also use distilled water temporarily. Let the engine cool off sufficiently, and then carefully open the radiator cap. Keep in mind it could still be under hight pressure. Cover it with a rag or towel to avoid getting burnt. Fill up the radiator and the overflow tank. Check if you see liquid leaking anywhere. If there is no leak, then most likely coolant escaped the system through overflow tank as a result of overheating.
#6. Check radiator fan. Both engine and AC system in your car are getting cooled off by passing liquids through the radiator in the front of the car. Normally when you drive fast - radiator gets cooled off by the incoming air. When you stop, the fan turns on to cool the radiator. If your fan is broken and you are not driving fast enough - the engine coolant temperature and AC refrigerant temperature will start rising. As a result - AC will stop blowing hot air, and your engine will start overheating.
To test the radiator fan, make sure the engine temperature is low and turn on the car. Turn on the air conditioner. Look at the radiator fan and make sure it is spinning. If not - it is likely broken, has a blown fuse or damaged wiring.
#5. Check the engine oil. Make sure that the level is good, and that the oil is not burnt, gunky or discolored.