* Ask good questions. The interviewer may judge you based on the questions you ask. For instance, don't ask "What does the company do?" Instead, do you research before the interview.
* Ask open ended questions. Stay away from questions that elicit yes/no answers from the interviewer. The information will have limited usefulness, and it'll break down momentum and rapport between you and the interviewer.
* Keep it positive. Don't raise sensitive or controversial topics. For instance, the interview is not the best time to inquire why 2,000 people were laid off last week.
* Don't assume you have the job. Don't ask about vacation time or other corporate benefits. You may come across as arrogant because your questions assume that you have the job. Save those questions until after you've received the job offer.