I have had 2 or 3 of my songs recorded and people seem to like what I write but I wouldnt begin to tell someone else what to do or how to write. What I have found helpful in the couple of years is people give me a song challenge - write a song with x word in it and make it rhyme or write a song about a certain person or theme or event. Its not that they end up particularly good songs but it gives you practice to develop your own style and to play with words and rhythm etc. Practice your craft and you will develop a style that you are comfortable with - classes might encourage you to write more or might put you off - only you know if they will help you.
I was once told a song should be able to tell your story in three or four verses but look at some of the most well known songs - they go on forever. There are no rules in music