Very tough and elaborate. The interviewers had nothing much to say. I knew some interviews might be in brief, but my employer asked so many personally heating questions which I felt embarassed, it was not a good sign. I thought an interview should be a half hour at the very least, but in fact it was more than three hours & two times.
When they just seem disinterested/like they are just going through the motions.
When they ask questions that have nothing to do with the job and/or ask very few relevant questions.
When they do not tell you much about the job, the starting date, etc.
When they indicate they do not know something they should have, meaning they never read your resume-I had an interview last year where I drove an hour and as soon as I sat down, they said I lived too far. My town is usually well-known; it was obvious they had not noted where I lived.
When they ask questions, you answer, and they do not seem to like your answers.
When they do not write anything down/have no notes, your resume there.
When they are really late-keep you waiting for the interview for a while.