Every conversation has an Instigator and a Responder 

This is an essential understanding for every actor. In a two-hander scene one character will be the Instigator of the conversation and the other will be the Responder. As it is in life, each of those roles will use different forms of conversation. The forms generate specific patterns of behaviour by guiding the actor's choices producing a lifelike consistency. This consistency of makes a performance both real for the audience and easy for the actor.