He must begin to analyze the character from what has been given in the script, and begins to build in his mind the picture of the character he is going to create. Usually the playwright will give a short description, but most of the information will come from the lines the character speaks. This is where the actor's thinking process must be sharp and thorough. People reveal what they are like by the things they say. Timid people have a timid vocabulary.
Braggers have a bragging vocabulary.
The actor is also a psychologist who tries to study the personality by the choice of words that are said. When he has given a why answer for all the words he will speak, he has solved the motivation. On stage everything said and done must have a motive. If there is a logical motivation for everything in the script, the actor will never be confused. Or what is worse, never confuse the audience.