According to Adam Seabrook, human resources consultant, executives tend to agree that the first 30 seconds of the interview are the most important to make a good impression. That's because an interviewer can form a strong opinion about you in that time frame.
Making a good impression is something that begins before you even enter the interviewer's room. It is very important to be kind, confident and objective right at the beginning of the interview.
If you accidentally place a 20 gauge shell in a 12 gauge shotgun it will most likely cram the barrel. This can very seriously injure the person using it and the gun immensely.