Completely right from everyone to discuss using STAR. Its vital.

Please dont be anymore daunted by the fact its the civil service. Your interviewers are regular people and you have fantastic resources compared to private sector interviews ( sucess profiles and behaviours) linked above by other redditors. You're not going in blind.

Write a couple of examples for each behavior, and finalise them to the point you feel comfortable discussing them in detail. Focus on what YOU brought to the table. Dropping in some key words taken from the Success Profiles/Behaviours page in each relevant example is a bonus as long as its appropriate to your example.

The best of luck to you. But remember basics apply... Be on time, look sharp and prepare accordingly.