The process of writing out the answers engraves the answers in your mind. Once in the interview they'll flow out freely and give you a significant air of confidence. Have at least two anecdotal stories on hand that you might work into an interview. These may highlight how good you are at the functions you think they are going to ask you about. Work them in, even if you're not asked specifically about the subjects of the story.
First impressions are crucial.
Even if the atmosphere is business casual, wear a suit or nice clothes. Clients are always looking for a reason to reject someone in the same way that recruiters will throw away a person''s resume for a single spelling mistake. Don't give the client a reason to throw you away. Handle yourself well. Answer honestly, but positively.