If you’ve landed an interview for a federal government job, chances are you’ve already been down a pretty long road.

You’ve successfully prepared a federal resume, answered the government’s KSA questions, filled out a detailed questionnaire, and waited . . . and kept waiting. Finally, you’re ready to strut your stuff before an actual interviewer. How do you prepare? Just like you would for any job interview -- and then a bit more.

“There are probably more similarities with a federal interview and those in the private and non-profit sector than most people think,” says John Palguta, vice president of policy at the Partnership for Public Service. “But there are some very real differences.”

Navigating those differences successfully could help you distinguish yourself from loads of other qualified candidates. To help you do so, here are some tips for making a name for yourself -- for the right reasons -- in Uncle Sam’s office.

Show Them Why You Want It

Many who work in government truly believe that being a public servant is a calling, not just an occupation, so hiring managers may want to know why you want to work for the government. “A good federal interviewer will want to know about your desire and motivation for your public service,” says Palguta. “If a person is really good at what they do then they will have higher-paying opportunities outside of government. You need to be prepared to answer why you are interested in public service.”

Prepare for Some Tough Questions

Government agencies are increasingly requiring some level of security clearance or background check before you can become a federal employee. Depending on the agency, you may be asked questions related to criminal history, drug usage or other security-related concerns either in the interview or at other times during the process. Be prepared to answer these questions truthfully and to undergo a background investigation and the associated adjudication process if offered a sensitive position.

Arrive Early

“Security is tight,” says Palguta. Many government agencies have increased security tremendously in recent years. Almost all require each visitor to sign in with security; others require you to go through metal detectors, receive visitor’s pass and even be escorted to your interview by security.

At the Pentagon, for example, Palguta suggests allowing at least 45 extra minutes -- but don’t expect your interviewer to understand that you were held up at the gate. “If a person shows up 10 minutes late for an interview for any reason you are starting the interview with a negative impression,” says Paul O’Donnell, deputy communications director at the Naval Criminal Investigative Service (NCIS).

To ease the stress, says NCIS Recruitment Division Chief Cheryl Marsh, ask your contact at the agency to clue you in on what you might expect beforehand.

Be Ready to Work

Depending on the position, you may expect a tiered interview process involving different types and several rounds of interviews, questionnaires and writing tests. NCIS special agent candidates, for example, begin with a prescreening interview with a senior special agent trained in interview techniques, according to Marsh. If the person passes the prescreen interview, he or she will have a panel interview with three special agents that may last for four hours. Other tests round out the process.

The details of each interview will vary based largely on the preferences of the hiring manager -- and also may depend on the level of the position. For lower-level jobs, you might only need a phone interview followed by one on site. “For senior executive positions I have seen up to four or five interviews, including meeting with a panel and even the agency head,” says Palguta.

You can gather some information about the process early on. When human resources calls to set up your first interview, ask them what to expect -- then repeat the question as you leave your first interview to gain insight into potential future rounds.

Do Your Homework

Career experts always advise interviewees to research the organization they are interviewing with, but it’s especially important for federal jobs. The reason: There is so much information available on federal agencies the interviewee has no excuse not to be prepared and be ready to ask substantial questions of the interviewing.

Check the web for recent news, says O’Donnell. “Do a simple Google news search by the name of the agency. What are the current issues they are grappling with? More than likely these will be on the mind of the interviewer.”

Then keep surfing. Beyond agency Web sites, Palguta recommends looking the agency up on sites including Results.gov, BestPlacestoWork.org from the Partnership for Public Service and the Web sites of the Office of Management and Budget and Government Accountability Office, where you can learn about how they rate as a place to work, recent reports and appropriations and other data.

“As a hiring manager,” Palguta adds, “I will be very impressed if someone is asking me thoughtful questions.”

You can also avoid painful errors. “If someone comes into our interview and says they really want to work for the military,” says Marsh, “they just got a big black mark because we are not the military.”