If you are an architect you will depend on a blueprint to structure the perfect house. You may sell more than one house that uses the same blueprint, but each time you build a house from your blueprint you vary the décor and landscape for variety.

Make up a 'blueprint' (outline) for each class format that you teach. Each song in your outline works toward one objective. Since most songs are 4 minutes long you will need 12 songs. With a couple of breaks between your most intense songs, a break to check heart rates, and a break to set up for floor work, the class should be 52 - 56 minutes long. Your class outline should never be longer than 56 minutes (including the stretch at the end), since you will need extra time for explanation, water breaks, heart rate checks.  You should always leave a few minutes between the present class and the next class coming in.  Running over is unnacceptable.

Each song in your outline has 2 elements - a standard (the choreography you will use) and an objective (purpose for doing what we are doing.)  For example, in my Drills classes we always warm up with walking lunges and active stretches.  The standard is type of movement (walking lunges and active stretches.)  The objective is the purpose for the movement (warm up without using any complicated choreography.)

The standard and objective for each song doesn't change.  My Drills classes always start with walking lunges and active stretches.  What does change, though, is the song I use for the warm up, and how I coordinate the music with the movement.  The structure and content of the song will dictate how I use the standard movements for the warm up.

For an example of a class outline see the athletic drills class outline at http://www.fitclasses.com/drills_class_outline

So - if it's a step class, write an outline that uses basic choreography for each song.  Think about a standard movement and an objective with each song. Maybe the fourth song in your outline uses "L" steps, the fifth song works split lunges, etc. 

In a cardio class your objective will usually be to elevate the heart rate so don't be afraid to use a multi-tiered objective.  For example, the second song in my step outline always uses stepping up lunges.  I call this my 'lower body strength' song.  Even though I am technically working cardio, the quads and gluts get fatigued during this song.  So it has 2 objectives, raise the heart rate and fatigue the thighs.  Although the music to Step song #2 can change, the standard movement will always be some variation of stepping up lunges, and the objective will always be to raise the heart rate and fatigue the thighs. (click here to download this routine)

Once you have written your outline and identified a standard and objective for each song it's time to choose the music.  The next link gives great suggestions for finding music, but basically you are going to look for music that facilitates each objective.  Pay attention to BPMs, mood and attitude.  For example, 'Eye of the Tiger' is a great upper body strength song (pushups.)

Use the CD 7 - 10 times before changing it. When you are ready, change some or all of the music, but stick to the outline. Keep the choreography for the new songs similar to the songs they replace in the outline.