METHOD 1

Drop a tiny blueberry sized piece of mixture/batter/dough or whatever it is you are frying in hot oil and if it quickly sizzles up to the surface you know your oil is hot enough.

METHOD 2

Drop a small piece of bread in hot oil (about an inch in size). It should take about 30-40 seconds to brown and you know your oil is at the right temperature.

METHOD 3

Dip the end of a wooden spoon or chopstick in the oil and if the oil starts sizzling and bubbling around the stick, the oil is hot.

Happy Cooking :)