Following are basic questions you should be prepared to answer (they will be asked in a variety of ways) before going into your job interview.
Practice with a friend ahead of time!
Why are you here? Why were you interested in this job?
What can you do for us?
What kind of person are you?
What distinguishes you from the many other people who are applying for this job?
Can we afford you?
In addition, thoroughly research the organization, and be prepared to respond thoughtfully to some aspects of the mission and operations of the organization.
Coming prepared with questions of your own also shows them that you are thinking for yourself and have something to offer. Some examples to consider:
What does this job involve?
What are the skills a top employee in this job would have to have?
Tell me about the office environment and the kinds of people I would be working with.
What would my supervisor expect of me in terms of communication and reporting back on my daily or weekly work progress?
When should I expect to hear back from you about a decision?