Develop knowledge about a sport or sports. Begin coaching at a young age. Early on, pick a mentor and learn his or her ways of coaching and handling young people. Volunteer to coach youth leagues. Even at this level, begin to network.
Protect your reputation as a coach who has his players' best interests as a primary priority. While this is obviously an ethical stance, it also goes hand in glove with a long-term winning philosophy. Sacrifice of standards for short-term gain can easily short-circuit a coaching career.
Move from youth leagues to assistant positions at the high school level. There was a time when all high school coaches were also teachers, but this is no longer true. There are more opportunities for coaching at a high school level open to non-teachers than ever before.
Immediately become a member of your state athletic association and coach's association. While this is not required for some assistant coaches, it is an indication that you are serious about your coaching future. It also is another avenue for networking within the ranks of the coaching community and the community of athletic directors.
Take the courses necessary to qualify for the testing that will certify you as a high school coach. These criteria vary from state to state but are available at each state's athletic association website. Continue to work your way up the ranks of assistant coaching, moving between schools if necessary.
Continue to attend regional and national coach's clinics. Not only does this offer you the chance to stay abreast of new developments within a given sport, it also further augments your ability to network. Begin to lobby for a head coach's position by letting athletic directors know that you are an interested candidate.
Seek out any reasonable head coaching position that becomes available. Even unsuccessful attempts are advantageous because of the experience offered by going through the process and the exposure as a potential candidate. Eventually, your persistence and the background you have built will be rewarded with your own position.