As basic mechanical knowledge, how should a driver correctly check the engine oil level using the dipstick?

1. While the engine is running and hot, checking that oil covers the entire dipstick
2. By listening to the engine for unusual noises only, without removing the dipstick
3. With the engine off and the vehicle on level ground, reading the level between the minimum and maximum marks
4. Only a mechanic is permitted to check oil level; drivers should never attempt it