• Correct it. Once you leave the room, your fate is sealed. If you know that things are going badly, you can try to put the interview straight. A willingness to admit mistakes is not going to harm the impression you make.
• If you know where you went wrong, then say so to the interviewer and tell them what you meant to say.
• If it is a more nebulous feeling that the interview is running away from you, then ask the interviewer outright how the interview is going, and are there any issues you can address. Tell them that you don't feel you have made the right impression and provide the evidence of the impression you meant to make.
• It may well not work, but if you really have blown the interview, what have you got to lose?
• Don’t over close the interview. This is a trait that is often seen in recruiting sales professionals.