How to distinguish between Thermistor, Varistor and disk capacitor?
How to distinguish between Thermistor, Varistor and disk capacitor
  they usually looks the same...


The best practice is know what you buy and keep items packaged up separately then you don't need to try and distinguish item A from item B. If you are trying to recover items from an unknown PCB i.e. you are hoping to salvage used (and possibly broken) components then my advice is this.....

Don't waste your time trying to save a few pennies because, almost certainly you will waste more value in lost time than money saved. Buy new items and look after them.