Explanation: The rhythm method I refer to is to uncover the driving groove that the melody, in a sense, asks for. There are accents, there are emphases in the melody. They help you identify the " drive" in the song, the rhythm grooves in the composition. There can be variations on it, and using these variations will make your arrangement original and interesting. Find the method, then you will give out the rhythm parts to the drums and rhythm section later. This step is the detective work.
A good way to discover effective rhythmic grooves is to simply tap along to the music. As you hear the melody in your head, tap your finger on the nearest table. That will give you the simplest and catchiest rhythmic grooves for the song. Then, write it down in what ever notation you will be able to understand. There will often be different variations of the grooves in different parts of the song. That keeps things interesting, so notate those variations.
Record your grooves on a MIDI sequencer program, if you can. Simply take a drum track, and record your tapping on one percussion sound.
Next: 5. Plan your counterpoints.