Contact your local dance instruction center to find out if it offers a reggae dance class. If you aren't able to find a local class, buy an instructional DVD. Either way, you will likely start by listening to the music and bending your knees to the beat. Then you may begin alternating the knee you bend to the beat and bobbing your head while shrugging your shoulders. Dedicate three hours or more per week to learning this dance style. Within three months of learning, you should have an understanding of the basic moves.
Practice at home. Whether you are being instructed by a professional at the Top Hat Dance Studio or following an instructional video, you will need to practice your moves in order to master the dancehall technique. Once you have the technique down, make the moves your own. Reggae dance is meant to be an expression of your feelings, so make your movements and calm or wild as you'd like. Since this is not a rigid style of dance, you may modify moves to your liking.
Show off your skills at the Reef Caribbean Lounge or reggae night at Third World Lounge. Here you can learn through watching others while practicing your moves.