In writing an arrangement, a basic choice is what the structure of the piece will be. By this, we mean what role the different parts play in the piece. You can write all parts homophonously. Or you can let one of the parts sing the lead and have the other parts sing accompanying lines.
Much can be learned from writing a single song using these two structures. This helps you to clearly see the effect of the techniques on the sound of the piece. In this blog there is an arranging exercise for that. The song we are using is Fields of gold by Sting. The exercise is to arrange the notes twice. First, in four parts, satb homophonous. Second, in five parts, in which the melody is sung by soprano 2 and the other four part sing homophonou accompaniment.