With the "tell me about a time" questions, they are looking for examples of when you have done something in the workplace to demonstrate a behavior (or competency) that they feel is a requirement for this role.

To prepare the sorts of competencies that they looking for, look at the job ad or position description (if you can) and look at the requirements for the job eg, excellent verbal communications skills, problems solving skills, customer service skills

Then in preparing about your responses use the SAO method - describe the Situation (what was going on); the Action (what did YOU do in the situation) and the Outcome (what happened as a result of your action). This is how you should respond to these questions to give the interviewer a full picture of your competence in that area. The example doesn't have to be anything life changing but it does have to be YOU doing it. Make sure you respond with "I" did not "we" did as they want to know about you specifically.

Some other questions that you might want to prepare are
- Why do you want this job/Why did you apply?
- Why are you the best candidate?
- What are your strengths/weaknesses?
- Do you have any questions about the role?