So you've coached for a while in Pop Warner ball and you love doing it and you want to take it to the next level. How do you break in to the "club"? It may not be as difficult as you think, if you are prepared and polished. But there are also things that go along with it that you need to be prepared for.
First is the question of timing. When do you get the job openings? Most High School programs like to have teachers coaching, plain and simple. Any jobs people are talking about in the November-February range are probably going to go to teachers. There are advantages and disadvantages in this for the school, which we'll get into later. But the jobs that are still unfilled going into the spring and summer are the ones that the school has attempted to fill internally and can't. These are the ones a prepared external coach can get.
The next thing is to apply for the job. I cannot stress preparation more here! You need to be much more prepared than for a regular job interview. You are not only going to be judged once, but twice - in your professional career and in your coaching career. You definitely need two résumés. If you're applying for a Head Coach job you'll also need résumés for all your assistants. Finally, you'll need an interview strategy - a "game plan" to control the situation and show your skills in the best light.
I would never recommend applying for a Head Coach job without a staff in place. If a school is looking for a coach, and is in a time crunch, they're going to want a guy that is ready to go pretty much on the spot. They don't want to take more time getting assistants sorted out before starting the heavy work.