A lot of companies are now using competency based interviews so you need to be prepared. Competency questions are about your behaviour and are a way for the interviewer to predict how you will act in a situation in a more objective way.
The interviewer will ask you a series of questions along the lines of:

• Describe a situation when you…
• Give an example of a time when you…

They vary from a standard interview which may be more of a conversation or information gathering. Competency based interviews are more systematic with questions targeting a specific skill or competency. You will be asked questions about your behaviour in specific circumstances, and you’ll need to give situational examples.

Ideally you will have been provided with a Job Description and Person Specification to help you prepare for the interview. Use this to focus on the skills and competencies they’re looking for. Look back at your employment and personal history to find a couple of examples for each that show you’ve got the relevant skills and strengths in each area to achieve a positive result.

For example, if you think you’ll be asked questions about your communication skills, find an example of when you resolved a disagreement, gave a presentation or taught someone how to do something.

Use the STAR technique (situation, task, action and result). Put together a sentence to describe each of these elements and remember the result or outcome is the most important bit to show you learned from the experience.

• Think of a Situation where you applied the competency
• What was the Task required as a result
• Explain the Action(s) you took to fulfil the task
• Highlight the Result of that action

Some key competencies include:

• Communication skills
• Decision making
• Teamwork
• Leadership
• Problem-solving
• Responsibility
• Organisation

Some typical questions and what they’re assessing:

• Tell me about a time when your work or an idea was challenged and you had to deal with conflict.
  Individual qualities – adaptability, compliance, decisiveness, flexibility, resilience, tenacity, conflict management, empathy, teamwork, independence, risk taking, integrity
• Describe a situation where you had to lead a team through change.
  Managerial skills – leadership, empowerment, delegation, influencing, strategic thinking, organisational awareness, project management and managerial control
• Tell me about a time when you came up with a new solution to a problem.
  Analytical – decision making abilities; innovation and creativity, problem solving, practical learning and attention to detail
• Describe a situation where your communication skills made a difference to the outcome of a situation.
  Interpersonal – Social competence and communication (verbal, listening and written).
• When did you feel the greatest sense of achievement at work?
  Motivational – resilience, motivation, result orientation, initiative and quality focus.

Some more examples can be found here:

http://www.theguardian.com/careers/careers-blog/star-technique-competency-based-interview

http://www.kent.ac.uk/careers/compet/skillquest.htm