There can be a number of potential problem areas when it comes to interviewing which come from the company themselves. This is generally rare, but knowing that it can happen will equip you to recognize and deal with the potential problems later on.
Primarily, the problems you’ll see with companies is poor communication. This doesn’t necessarily mean the entire company is bad; it could just signal that one individual within the company has poor communication practices.
It would be foolish to think that someone at the company is sitting around for you to send them an email or make a phone call, and they also have other work to get done within the company. Giving them the benefit of the doubt and having some amount of patience will be important.
If you have to wait more than a few days to get a response, this can signal a “red flag”, but be patient. They may be screening dozens or hundreds of applicants for a single role.
In my own experience, poor communication usually revolves around promising one thing and saying something different next time. When confronted, they’ll get defensive, and rarely be apologetic.
I’m a big fan of feedback, and iterating on that feedback. I’ve always told every candidate I interview that if they have any feedback about the process to please pass it along.
I’ve heard unimaginable stories from people, usually non-male though sometimes non-white males, who have an extremely bad interviewer. Please know this is the company, not you. If you face something very horrible during an interview, you should send feedback to your point of contact as soon as possible. While it may not help your chances of getting a job at the company, you might not want to work there anyway if the company is allowing this behavior. Then again, the company might not know that a particular interviewer behaves this way, and without your feedback they cannot correct anything.