Talk to the person who is leaving the job. Find out the key issues, core competencies, what skills and abilities, both "hard" skills and "soft" skills, they are looking for.

Go through the interview questions with this information in mind.

Write down answers to questions that will require detailed information or that you might forget in an interview panic, e.g. software competencies, databases you use.

Prepare in advance what questions you will ask the interviewer(s). See this about.com page http://jobsearch.about.com/od/interviewquestionsanswers/a/interviewquest2.htm for details.

After the interview, send a thank you for the opportunity to interview.