1. Be on time - not early and definitely not late. Dress appropriately for the building and the neighborhood it's in. When in doubt, business casual is usually a safe bet.
2. Be prepared - bring a copy of the board package with you and make sure you are intimately familiar with it as well as with your own financials. Be ready to answer questions about your financials and be prepared to substantiate claims made in your application package.
3. Be boring - less is more. The board is interviewing you, not vice-versa. Do not elaborate beyond straighforward answers to the board's questions, do not volunteer information that the board did not ask for and do not ask questions of your own. In general, a short interview is better than a long one.
4. Be a joiner - boards look for candidates that will be good neighbors and rule-followers, that will fit in well in the building and that will volunteer to serve on the building's committees or on the board in the future.
5. Be an open book - unlike a job interview, boards can and will often ask very personal questions. You should be prepared to answer these questions, unless they violate Fair Housing or New York City Human Rights laws. Put on a smile and be yourself, appearing to shy away from these questions or to be upset by this intrusion makes you look like you have something to hide.
6. Be a team - usually, every member of the household will be asked to attend the interview. Decide in advance who will take the lead at the interview and who will answer what questions. Do not discuss answers to questions during the interview, do not contradict eachother and do not argue amongst yourselves during the interview.
7. Be well rehearsed - a good broker will go over the questions you will likely be asked and will allow you to rehearse your answers with him/her before the interview. Practice makes perfect and rehearsing your responses will help you put your best foot forward.
8. Be satisfied - do not discuss the major renovations you have in mind for apartment and do not ask when the building intends to spruce up the lobby and common areas. If asked, you can say that you think you will re-paint the apartment or put down carpet in the bedrooms, but remember, extensive rennovations for you means months of noise and commotion for your neighbors.
9. Be committed - be enthusiastic about the building and the neighborhood. Everyone wants to be desirable, and a good answer to the question "why do you want to live here?" can go a long way toward getting you in.
10. Be patient - do not ask for, or expect, a decision on the spot. Usually the board will notify you of their decision within a few days.