The song writing process can be started by either the words or the music. The process is more natural through practice and often is a process of going back and forth between building a relationship between the words and the music. If writing an instrumental piece of music some of the rules still apply.
Writing words. This is one method that can be used.
Generate song ideas and words connected to that idea. - Use a mind map, use a free flow of thinking
Sort - Categorise Words
Identify 6 significant words to your subject
Connect - Create the 4 best lines of lyrics you can create using two of the significant words in each line.
Elaborate - Connect the lines to make sense- refine to become a verse in the song.