Don't act nervous, tapping fingers, wagging your legs or wringing your hands (crossing ankles or arms is considered defensive/in a standoff), nor sitting stiffly as a statue, but also not flopping around like you're lazy (silly or too relaxed). If you're asked to answer a case (what if...) question, talk through the process you would use, in such a case. Don't be afraid to ask whether your ideas sound thorough enough—you'll be evaluated on your ability to structure your thinking and to share your thoughts well, not on the number of questions you ask. In fact, talking through your process is a great way to engage the interviewer and turn the interview into more of a give and take discussion. This can give you valuable clues and a guide on what they want to know (so you can show how you can fulfill their needs).
- If you need something clarified, don't be afraid to ask. You'll do better, if you know exactly what is being asked of you. Don't ask a question every few seconds, or you'll sound confused (you want to show that you have good motivation toward what's good, reasonable and logical).