Check for oil level after filling petrol; you can notice that after having filled the car with some 98 RON, paid for your petrol [a matter of 4 minutes], restarting your car gives you instantly your oil level automatically.
Apart from this situation, check the level when the motor is warm, and the car on a flat surface.

Also,
coolant level: when the engine is cold, on a flat surface
Hydraulic fluid reservoir for power sterring: cold engine, on a flat surface
Brake fluid level: cold engine, on a flat surface