1. "Sorry I'm late; it's hard to find a reliable babysitter." First, you shouldn't be late. But beyond that, don't make statements that will make employers worry that you'll have trouble keeping your family commitments from impacting your reliability at work. Employers do understand that people have families, but if family interferes with your ability to show up on time for an interview, they'll assume you'll frequently be late or absent from work too.
2. "I'm planning a month-long trip around the holidays." If you have pre-planned vacation time, the time to raise it is once you have a job offer—at which point you can make it part of your negotiations. But announcing you'll be gone from work for a month while an interviewer is still making up her mind about you is a good way to having your name crossed off the list.
3. "I hate Republicans/Democrats/Libertarians." Unless you're interviewing for a job in politics, statements about your political beliefs don't belong in a job interview. No matter what clues you might think you're getting about your interviewer's political affiliation, you can't know for sure, and you risk alienating her. Or you might simply come across as someone who doesn't have the sense to avoid hot-button topics in a business conversation.
4. "My dream job is to work on a cruise ship, teaching pottery." Unless you're applying to work on a cruise ship or to teach pottery, this answer will set off alarm bells for employers. Interviewers want to know that the job you're applying for fits in with your longer-term career goals. Otherwise, they worry that you won't be satisfied with the work and/or will leave as soon as a path to your dream job comes along.
5. "I'm pregnant." Although it's illegal for most employers to discriminate based on pregnancy, plenty of interviewers are still going to think, "We have an important event right when she'll be out on maternity leave, and candidate B, who is not pregnant, would be able to be there for it." Don't risk that happening. Wait until you have a job offer before you mention your pregnancy.
6. "My last boss was crazy." You last boss might have been utterly insane, but the business convention is that you don't speak badly of previous employers in a job interview. No matter how correct your assessment of your old boss might be, you'll raise a red flag for your interviewer if you badmouth her.
7. "Wow—your receptionist is really cute." You might as well just announce, "I'm going to sexually harass your staff if I get this job, because I don't understand professional boundaries."
8. "No, I don't have any questions for you." You'll be spending at least 40 hours a week in this job, and there's nothing you want to know? If you don't have questions for your interviewer—about the work, the team, the culture, and so forth—you'll signal that you're either not very interested or not very thoughtful.
Alison Green writes the popular Ask a Manager blog, where she dispenses advice on career, job search, and management issues. She's also the co-author of Managing to Change the World: The Nonprofit Manager'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.