I just spent the day interviewing ppl for a clerk position with the government agency I work with. You want to be prepared! (Obvious I know) but take some time and try to do something like this:
1- Look at the agency / company website, figure out and memorize (as much as possible) exactly what they do (their mandate) their corporate values.
2- Research the job position, pick out the central traits they are looking for (normally something like: respect, tact, observational skills, people skills), as well as the main duties.
3- Search (or ask a friend) to give you sample interview questions. Monster is great resource, as are many other career websites.
4- Write everything down. Expect the basic questions like: "How are you in stressful situations, let’s say the phone is ringing, there is a line of 5 people waiting to see you, and your boss is expecting you to finish a report by end of day" ; basic team work question "A colleague comments that the new person in the office wears too much cologne, is under performing, and does not seem to grasp the consequences of the backlog she is creating, how do you handle the situation" (etc, etc)
5- PRACTICE - remember those values in comment 2, try to use those exact words as often as possible, guaranteed they are looking for it!
**** Have a good nights sleep**** easier said than done....
6- Bring an extra copy of your resume, and a typed up page with your references.
7- East your normal breakfast, skip the caffeine, and arrive at least 10 minutes early.
8- Always ask questions at the end, however, I don’t suggest you ask about salary. Advancement, daily tasks are a good starting point.
9- Send a thank you email or phone call 1 week after. Ask for constructive criticism, it displays initiative.
Let me know if you want more interview questions, I know so many, we can set up an interview online
Best of luck!