I was talking recently with someone who is interviewing for a job at the Pentagon, and I thought I'd share some general tips. The Pentagon, as you all know, is vast, but here's generally how I would approach an interview there:
1. Have some questions to ask about the job (logistical, substantive, etc.) but don't force the questions. A position like this is designed for an intelligent, inquisitive person, but they don't want someone who is forcing it during the interview. At the same time, they aren't looking for workers who are hoping to land a job at the Pentagon so they can tell everyone they work at the Pentagon. Interested, but discreet, should be the approach.
2. Call ahead to get precise directions (if you don't have them already). Federal buildings with high levels of security are like mazes, and the last thing you want to do is show up late. Find out about parking, contact phone numbers, whom to ask for, etc. (This one is really an all-purpose interviewing tip.)
3. Do not wear lots of watches, jewelry, cuff links, etc. It sounds cliché, but they do like people with a buttoned-down, respectful appearance (read: conservative).
4. Do not bring a cell phone. Most of the time these buildings restrict them, and bringing one in your pocket will just require you to return to your car to drop it off or leave it with the security people (either of which could make you late).
5. If the interview is with a military person, feel free to use "sir" and "ma'am" in conversation (where appropriate). Though you are a civilian, the token effort to show respect to the uniform goes a long way. Even the civilians in the building will appreciate it, so while you shouldn't overdo it (it's not boot camp), it's something to keep in mind.
6. Use a firm handshake, look people in the eye, and try to avoid using words such as "like," "you know," etc. (Another all-purpose tip)
7. BE KIND TO THE STAFF. If you're shown into an office to wait for the interviewer, be friendly and cordial to the admins, secretaries, etc. If the staff doesn't like you, it can sink your chances at the job,even if you gave a great interview. (Another all-purpose tip)
8. Avoid political chit-chat. You don't need to swear allegiance to GW Bush, nor should you speak critically of either political party. It's unlikely that you'll be discussing politics in the first place, but don't force a political discussion just because you're at the Pentagon.
Edited to add: See update on the interview here.