Possess an adequate amount of musical ability that includes being a competent music sight reader. You also should have a sense of rhythm and a familiarity of different instruments and their role in a musical piece.
Practice every day. Write down the skills and techniques you want to work on during each practice session.
Observe your competition at local sporting events and parades to get an idea of what you should and should not do as a drum major.
Participate in drum major competitions for single performers to sharpen your skills and shed your fears.
Dare to be different. Experiment with new and diverse techniques that will lead to your own personal style of conducting.
Spend time at a summer camp or workshop for drum majors. Experience a variety of conducting/performing styles and teaching methods. Search online to find a camp near you.
Opt for one-on-one instruction with an experienced professional. This is a surefire way to elevate your skill level.