Here are 10 tricks interviewers often use that can trip you up if you're not careful:
1. Silence. Some interviewers will intentionally remain silent when you finish an answer, waiting to see if you'll start talking again. Most people are so uncomfortable with silence that they'll rush to fill it, and in doing so, they might offer information that's too candid or maybe damaging. The best strategy here? If your interviewer is using silence on you, remain silent right back. Chances are good that after about 10 seconds, the interviewer will start speaking again. If not, you can always ask, "Did I answer your question fully enough?"
2. Extreme friendliness. Good interviewers want you to let your guard down. By putting you at ease, they can get a better sense of who you really are (which is probably good for you) and maybe get you to relax and slip up (not so good for you). You're more likely to reveal something unflattering if you feel comfortable. This doesn't mean that you shouldn't relax, but do realize that this isn't a cozy chat with a friend; it's still an interview.
3. Asking "What do you know about us so far?" Interviewers ask this because they want to know if you did your homework. If you haven't prepared for the interview by learning all you can about the organization, it will show.
4. Asking why you're thinking about leaving your current job (or why you left your last job). Interviewers want to know if you're leaving (or if you left) on bad terms, or if you're willing to badmouth an employer.
5. Asking how soon you can start. You might think that expressing a willingness to start right away will play in your favor. But if you indicate that you would leave without giving your current employer at least two-weeks notice, interviewers will assume you'll do that to them someday too. Instead, explain that you can start as soon as you give appropriate notice and fulfill your obligations to your current employer.
6. Asking you to follow up about something. If the interviewer asks you to follow up with some information—or takes you up on your own offer to send, say, a relevant article—make sure that you do it. She might be watching to see how well you remember and follow up on commitments, even small or informal ones.
7. Leaving you with the receptionist. Some candidates will say things to the receptionist that they'd never say to the interviewer—whether it's revealing candid impressions about the job, mentioning that they're hungover from last night, or flirting inappropriately. Smart interviewers will always ask the receptionist or others who came in contact with you for their impressions.
8. If you were laid off, asking if others were laid off with you. "How many in your department were laid off as well?" probably isn't an innocent question; it's an attempt to figure out if a past employer laid you off to avoid having to fire you for performance.
9. Asking you to describe your dream job. If you start talking about your true desire to work in film when you're applying for an accountant job or your hope to manage political campaigns when you're applying to be a teacher, most interviewers will think you're not especially committed to the position for which they're hiring.
10. Asking what questions you have. Okay, this one isn't really a trick, but a good interviewer can tell a ton about you by what questions you ask. Do you focus on benefits, pay, and hours, or are you curious about the job itself? Interviewers want to hear thoughtful questions about the work, the culture, and the organization—questions that show that you're really trying to figure out if this is the right fit for you.
Alison Green writes the popular Ask a Manager blog, where she dispenses advice on career, job search, and management issues. She's also the author of Managing to Change the World: The Nonprofit Leader's Guide to Getting Results and former chief of staff of a successful nonprofit organization, where she oversaw day-to-day staff management, hiring, firing, and employee development.