An interview is a two way conversation and the questions you will ask and answer should be carefully thought out before going to the interview in order to avoid offending the interviewer or causing the interviewer to raise an eye brow towards you in question.
Remember why you are there and keep all complimentary comments towards the company and not the interviewer. Complimenting the interviewer on appearance could create an uncomfortable feeling and raise a flag to the interviewer that you are trying to suck up in some way.
Do not bring up previous illnesses unless they are relevant to the job. A void in your employment record due to an illness could be relevant if you were recuperating from a surgery or a procedure that was long term. Let the interviewer know about it and that it has not been a problem since.
Leave out long discussions concerning problems at your previous employment and instead let the interviewer know that you dealt with problems by working through them successfully. Questions related to problem solving are asked because the interviewer is interested in how you handled them.
Never comment on items in the interviewers office to force a common ground of interest. The interviewer does not care if you have the same interests with them or not. You can make a comment that the company offices are nice and ask how long the company has been at that location instead.
If you were let go from your previous job do not tell the interviewer that you were fired. Using the word fired can change the focus of your interview to your bad attributes instead of your good qualities. Instead you can say you were not a good fit and explain what you learned before being let go.
Always have a list of questions to ask at the end of your interview. Not preparing questions can make you appear unprepared and uninterested in the job. This could make or break your chances at the end of your interview. Be sure to keep your questions related to the company and employment.