Here are the warning signals:
Uncouth behavior: Don't overlook unprofessional approach such as not responding to emails or changing the interview dates and time without any apology. This shows the working style of your potential supervisor.
Visual cues: While greeting you if potential employers scan you from head to waist and waist to head; it means that they are telling you that you are smaller than them. It is a belittling comment though subtle. Know that your talents are not going to be recognized there.
Disturbing body language: If your boss is consistently shifting or is avoiding eye contact or shuffling through papers when you talk, take it for granted that he is an insecure boss. Such a boss feels threatened by you and he will not allow you to flourish. He will make your life miserable.
Not the right attitude: If your interviewer doesn't show any interest in the company, he is a bad boss. Watch out for such people and be sure that you won't be happy with them.
Extremely nervous boss: Those bosses who consume large cups of coffee or eat raisins all the time are extremely nervous. Most of them speak in triplets: 'hi, hi, hi', 'good, good, and good' 'when, when, when'. The stress levels of such bosses affect everybody in the department.
Distrust: Toxic boss don't trust anybody. If such bosses are asked about the problems and their causes, they blame their team members. They lack trust in others.
Fear factor: Be wary of bosses who don't have respect for colleagues. When managers disrespect or distrust others' motivations they resort to threats, public humiliation and comments about layoffs.
Negative message: The choice of words creates the level of dynamism on the workplace. If your bosses begin every statement with a negative message, negativity prevails in their life and they carry it into your work.
Too friendly: Be careful of too nice a boss. Don't you know that often children are lured into dangerous situations? Same is the cases with too friendly bosses who lure you to situations you don't like to be in.
Dominating boss: If your interviewer says you are wrong and gives his answer to the question, and often interrupts you, he belongs to the dominating type. Be sure that you won't be able to work with him.