Interviews at time can be tough but then if you are prepared beforehand, there is a fleeting chance that you might actually get lucky and crack them.
one of the foremost etiquettes that you should keep in mind even before you attend an interview is to switch off your phone before you even present yourself in front of the panel. Secondly, make sure that when offering your hand for a handshake, your grip is firm and confident.
Make sure to give your interviewer a smile the moment you enter the room. keep it warm and friendly. it will help ease down the conversation right from the beginning.