Let's turn our attention first to what makes a song followable. A song is followable when your congregation can pick up on it easily, like on the second time through. A followable song will typically be a memorable song, and they will walk out the door with the song on their lips and it will stay with them through the week. Simplicity - With the exception of a handful of songwriters I know who can do this naturally, it takes skill to write simple songs. A simple, easily singable melody, a singular theme, a simple form, and a small amount of lyrics.
Simple melodies consist of simple rhythms with natural, flowing melodic movement.
Generally, the melodic movement should not consist of too many large intervals. Either they catch on or they don't. If you are blessed with a high voice, you need to remember that you belong to a minority. You may think this is too restrictive, but if you look at the songs that everybody sings, you will find that the melody range is small and low. Singularity - A song should be about one topic, such as God's love, grace, the Cross, mercy, intercession, unity, and so on.