I think being able to write is a bit of a gift,topped up with understanding structure and stuff like that.....i can only speak from my own methods and experience .
Writing for your own pleasure and writing for the industry are two completely different things.When i first started ,i wrote pretty much what appealed to me,now i'm focused on what makes catchy, saleable songs.
But whatever your motives are , to improve the quality of your lyrics, you must first become a better storyteller......you have to storyboard each scene,each sentence out in your mind... see the detail, and include some of it in the song.......and i can't emphasize enough to listen as much as you can,,preferably on Youtube (so you get the visuals as well) the music of your genre..and break it all down , then reassemble it,,see how it works,,how professionals do it.