Traditional Interview vs.
Behavioral Interview Questions

In a traditional interview, you are asked a series of questions which have straightforward answers like: 
 
    - "What are your strengths 
       and weaknesses?"    
    - "What major challenges 
       and problems did you face?
    - "How did you handle them?"  
    - "Describe a typical work week."

In a behavioral interview, an employer has decided what skills are needed in the person they hire and will ask questions to find out if you have those skills.

The fundamental theory of Behavioral Interview Questions: Your past behavior is an excellent predictor of future behavior. If the job requires excellent time management skills, the interviewer will therefore ask you for examples of where you had to use this skill in the past. The interviewer will want to know how you handled a situation, instead of what you might do in the future.  Following are example behavioral interview questions:
    - "Give me an example of a time when you went above and 
       beyond the call of duty."
     - "Give me an example of a goal you reached and tell me how 
       you achieved it."
     - "Have you handled a difficult situation with a co-worker or 
        teammate?  How?"

Answering Behavioral Interview Questions: 
The "STAR" Technique
One strategy for preparing for behavioral interviews is to use the "STAR"Technique, as outlined below:
S - Describe the situation or event you were in.   
T - Describe the Task(s) you performed.
A - What action(s) did you take? 
R - What was/were the result(s)?

How to Prepare for the Potential Behavioral Interview
You do not know what type of interview you will have until you walk into the interview room.  In general, it is best to prepare for traditional interview questions.  There are a few tips to help you prepare for the surprise behavioral interview question, however:
     - Consider special situations and projects you have dealt with
       in the past, and note details.
     - Frame responses and prepare stories that illustrate times that
       you have successfully solved problems and performed well.
     - Review the job description, if possible, and note the skills and
       behaviral characteristics that the employer is looking for
       (often found in the "skills required" and "qualifications"
        sections).  These are often the skills you will need to
       highlight in your behavioral interview question responses.

More resources on behavioral based interviewing:
Behavioral Interviews: A Great Showcase for You, But You Must Prepare Now
Complete List of Behavioral Based Interview Questions
Job-Employment-Guide.com
You Can Survive the Behavior Interview