The  interviewer not only has the right to ask about anything he or she deems to be relevant to the position being offered but also he or she is trying to understand your mental state and trying to asses how you will fit into an existing environment. But among these questions there are four most common questions are as follow:

 1- Tell me about yourself?
 2- What are your strengths & weaknesses?
 3- What experience have you had that qualifies you for this job?
 4- Why should I hire you?

 - Relax, the first question is straightforward, and is intended to put the interviewee at ease. Give a brief description of your experiences relevant to the job applied for, don't ramble. Use your resume summary as a base to start. The interviewer is not asking for your life story.

 - Prepare yourself  before the interview for the second question by reviewing your academic or work experience. Most people know their weaknesses but don't like owning up to them. The answer is to think positive. The key here is in the presentation. Example, "I work well independently." makes strength out of being a bad team worker.

 - Focusing on the last question should have prepared you to discuss positive experiences that qualify you for the position.

 - The fourth question is more than just another re-iteration of your strengths and skills. Employers are not only interested in past work experience; they also want to know you are dedicated and committed, that you are not going to be a disruptive influence and that you will fit into their company culture.

 Try answering the questions below before the interview. 
 What do you know about my company?
 Why do you want to work for us? 
 What aspect of the job do you find the most attractive? 
 What do you look for in a job?
 Why should we hire you? 
 How long would it take you to make a meaningful contribution to our firm? 
 How long would you stay with us? 
 What important trends do you see in our industry?
 Why are you leaving your present job?
 How would you evaluate your present firm?
What were your five most significant accomplishments?
Why haven't you found a new position before now?
 What do you think of your boss?
 What other types of jobs are you considering?
 If I spoke with your previous boss, what would he say are your greatest strengths and weaknesses?
 In your present position, what problems have you identified that had previously been overlooked?
How do you resolve conflict on a project team?
What was the most difficult decision you ever had to make?
How much do you expect, if we offer this position to you?
Do you generally speak to people before they speak to you?
Are you creative?
How would you describe your own personality? 
What are your future goals?