- Voice your approach as you go through it - remember it is a test of your problem solving skills than it is a test of the accuracy of the final answer
- Communication allows the interviewer to help you
- Do not ramble - do not add superfluous words or fancy words unnecessarily - remember that the interviewer is also testing your communication skills
- If an interviewer points out a mistake - be humble, be open to criticism. Remember that the interviewer is only trying to help you get to the correct answer. Graciously accept the correction and alter your solution accordingly. Show the ability to adapt to change and openness to feedback.
Voice your approach
This is perhaps the most important aspect of solving a guesstimate. Be in constant communication with the interviewer but at the same time do not ramble just to fill in gaps in communication. It is perfectly normal to take a moment to think and then give a structured response rather than make stuff up as you go.
Open to feedback
Communication is a two-way street. Always be open to criticism. Interviewers for the most part are helpful and willing to at least nudge you in the right direction. Of course, there might be cases where the interviewer is just trying to test you and in such cases, it is necessary to stand your ground but more often than not any feedback received from an interviewer is helpful and should be incorporated.