Not looking where you're going
When I took the job that gave me the unhappiest years of my life, I did so with hardly any previous research. Interview day was the first time I had even seen the school, let alone been inside it. I had no inkling of its problems or working culture, and no understanding of the kind of expectations that were placed on people at my management level in the school. Obviously none of the printed job details even hinted at any of that. I was a lamb to the slaughter.
What is the right thing to do? Tour the area and visit the school for at least half a day. Talk carefully to people at or near your proposed level. Assess their state of morale, their philosophy, their attitude to children and colleagues. Above all, be objective and ready to walk away. Don't just hear what you want to hear.