There are normally set elements to competency questions, things to do with team work, personal development, difficult situations etc. They require you to recall a specific situation from your past working career or even life.
Most interviews I've had have used the same format. Google is your friend. They'll ask
'Can you think of a time when you have found it difficult to settle into a team. How did you overcome this and what was the eventuall outcome?'
Or
Can you think of a time when you've noticed something that could be improved in the company. What did you do and was this implemented?'
They normal ask around five questions so I've been able to build stock answers and adapt them as needed.
Yeah, it's easy to forget that you are doing them a favor too buy turning up to the interview and doing your best!
Right, after all that it's time to go for the bus!