I always prepare notes for any sort of important situation. Even if they are not terribly meaningful notes, I can look back at them like a script of sorts. Another helpful solution is listening to yourself. Do not let your mind wander during an interview. Listen to what the interviewer is saying and what YOU are saying. Offer the interviewer a smile and an apology, collect your thoughts and move on. It's better to continue after having made a mistake rather than quit half way through.

You can take deep breaths and just clear your mind for a second. Doing this can help the interviewee in getting back on focus to being professional.

During an interview, I believe it is smart to respond to the question and try to restate the question as you wrap up your response to make sure you stayed on track and kept yourself from allowing your nerves to make you ramble. For example, if the question is, "How do you feel about working on a team?" provide a detailed response and then as you wrap up your response, restate the question..."I believe working as a team strengthens teaching practices and ensures students' needs are being met".

Try to remember why you are there, you worked hard to get where you are and you have nothing to be nervous about. Remember that you are the best candidate and be confident in the work you have put in.

This has happened to me. Being aware that you need to get back on track is a good start.