From your experience, what is the most common mistake candidates make in their first interview?

The biggest mistake is the cost of dialogue, dishonesty, lack of listening, and lack of timely access to the interviewAlso, you should not talk about the previous company or the former manager badly also not disclose the secrets of the previous company

Thanks

• Talks a lot
• Mentions some events that will affect on interviewer opinion negatively.
• Ask a lot of question not related to topic of interview.
• Does not care of his - her attitude, neatness, ...

saying something they dont exactly know. Or trying to be ovesmart.

it's imperative to look professional and polished. ... that you can make a bad first impression before you even arrive at your interview? ... the better you will be able to discuss your past experience during your interview

I don't believe in mistakes I mean mistakes are part of life and yes we are no one to judge anyone mistake if Allah forgets mistakes who are we. 

In interviews there are no mistakes, yes but there may be understanding issues with the employee or maybe employers it totally depends on the question asked at what atmosphere because the atmosphere plays a vital role in interviews. So its better to read well before interviews and understand the norms that's it.