1. Why do you want to work for us?

Answer
This question is about the company and needs you to do a lot of research on the company and more so on the specific role you're being interviewed for. Answer this question in two parts. First, demonstrate what you know about the company based on the research you've done and then tell them how you will be able to contribute to their success.

Maybe the company's flexible work practices or permanent part-time positions make it possible for you to combine employment with other commitments like study, sport or family life. Perhaps it's the opportunity to work for renowned senior practitioners in an area in which you are experienced or keenly interested.

Note: the truth may be that you'll work anywhere that pays. If you're desperate to find a job and you're not choosy, then you may not have given this question any thought.

Don't ever say "I just want a job and this is a job that I can do", or anything that suggests this. It may be true, but it won't help you. Every employer wants to feel that there is something special about his or her company and that you particularly want to work there.

2. What other opportunities are you considering at the moment?

Answer
This is something of a sneaky question because there's no one right answer. If you are being courted by other employers, you become a more attractive candidate to the person who is interviewing you.

However, you can answer in several different ways, depending on your circumstances. If you are happily employed and only attending the interview because this is your dream job or a company that you have always wanted to work for, you can make this point.

If you are not currently working or you are actively looking to move from your current position, you might boost your appeal if you note that you are considering other opportunities. The less said about the detail, the better.

Recruitment consultants will usually ask this question and for a practical reason. They may (but only after asking your permission) introduce you to various companies as a potential candidate. They don't want to end up looking silly by introducing you to a company where you have already been interviewed.

3. Did you find us alright?

Answer
This is probably the first question that you might encounter when the interviewer meets and greets you. The answer should be minimal.No unnecessary chatter. Say for example you found it difficult to find the place and are elaborating on it. The interviewer might think "if only this guy had researched it on Google maps before he came here". You are leaving lose threads for the interviewer to form an impression about you. If your answer was a simple yes or no the story ends right there.

Always remember the interview actually starts when you enter the compound of your future employer. Be courteous to every one you meet (not just the interviewer).

4. Why are you looking to leave your current position?
OR
Why did you leave your past job?

Answer
You will almost always get this question. Your answer should be in the lines of career improvement, or changes in the industry or organization (caused by technology, changing markets, downsizing), a desire to move to a new location or professional development. Never ever bad mouth about your previous employer (even though your boss might be an ass).
Be consistent, be positive and confident in how you present your answer.

5. Change is a constant in this organization. How do you respond to change in your environment?

Answer    
This may be a cloaked discriminatory question, asked of you if you are mature-aged and the interviewer has a stereotype that older people aren't flexible and adaptable.

Be direct, positive and don't get defensive with your answer.

Demonstrate experience: "I am very accustomed to change. My experience in X industry/in my position with X company illustrates this. For instance..."

Or demonstrate understanding: "I understand that organizations these days are operating in a very different environment compared to 10 years ago. It is important that companies are able to quickly respond to the changing needs of their customers, shareholders and suppliers. That requires employees who can find new ways of solving problems, who can keep their eye on the bigger picture, who don't get stressed by new procedures. So while I've worked in a quite stable environment, I have suggested changes to the way we ...."

Always remember your experience is your strength, show case that in positive light rather that answering it in negative mode.

The series of hubs have several interview question and answers.
Part 1 of the Series - Interview Tips
Part 2 of the Series
Part 3 of the Series
Part 5 of the Series