Your starting position on the chart is listed in a coordinate system of horizontal and vertical values.  Instead of an X and Y coordinate, this might be listed as a number of steps Left or Right (on either side of the 50 yard line) and a number of steps in front of or behind the hash line that runs parallel to the Visitor-Home sidelines.  Drill charts are read from the viewpoint of the director. If the chart says “in front of” it means toward the director. If the chart says “behind” it means away from the director's viewpoint. In order for the marching band to look uniform, it's important that everybody moves about the same distance with each step they take. Drill chart instructions will be listed in steps.  The standard marching style is called 8-to-5, which means there are 8 steps for every 5 yards. Since there will be 5-yard lines on a standard football field, it creates a grid marchers can follow, counting 8 steps between each line. You can also think of each step as being an average of 22.5 inches, since there should be 8 steps in 5 yards. This measurement is often used as a standard. More important than knowing the average size of a standard step while you're marching is to be moving at the same pace as those around you. Each position in a drill chart corresponds to a count in the music. As the song progresses, you will move across the field into a new position. You will start on the count of 0 and generally move in increments of 8.

Summary:
Find your position number. Move in equal sized steps. Follow the count.