Thermometer: the most accurate way to see if the oil is ready, is to use a thermometer. I recommend choosing one that is suitable for frying. The oil is ready once the temperature reaches 175°C to 180°C /347°F-356°F. Remember to check and maintain the right temperature during the frying to prevent the food from burning. Bread test: alternatively you can use the bread as a tester method. Drop a small piece of bread into the oil. If it immediately starts sizzling and browning, the oil is ready. if it sinks and doesn't sizzle, the oil is not hot enough. On the other hand, If it browns too quickly or burns, the oil is too hot. Wooden test: another way to test, is to use the handle of a wooden spoon or a wooden chopstick. Once the oil is preheated place the handle of a wooden spoon or a wooden chopstick into the oil. If small bubbles start forming around the spoon's handle, the oil is hot enough. If the bubbles are very vigorous it means that the oil is too hot and needs to cool off a bite. On the other hand, if no or few bubbles pop up, then the oil is not ready.