Something Connie said; "One thing I learned, is that you have to come up with the title of your song first. From there, you can keep your idea focused and you won't find yourself all over the place." I'd disagree slightly with that - the first thing you should have in mind is a good hook, whether it's a good line lyrically or musically. That hook MAY end up being the title....
One thing I HAVE learned is that no two people write a song the same way...for me, nine times out of ten it'll be a phrase I've read or heard that sparks my imagination. As I'm writing lyrics, I'll have a rough idea of a melody and/or chords in my head to go with the words...usually I'll have a guitar handy, which is even better.
When I've got that spark, that germ of an idea, I'll play around with it....I never quite know how it's going to end up, but hey, that's half the fun of being creative!
To digress slightly - Stephen King, in an article titled "Why I was Bachman" wrote the following; "....I never really planned anything big that I ever did, and that includes the books I've written. I never sat down and wrote page one with anything but the vaguest idea of how things would turn out."
OK, writing a three-hundred page novel isn't quite the same as writing a three-minute song - but there are similarities. You've got to tell your story, get the point across and keep the reader's/listener's attention.
I read a HECK of a lot - have done since I was a teenager, over thirty years ago. There's nothing better to improve your vocabulary, your word-power and your fluency. I think after a while the constant reader tends to absorb, consciously or not, some of the mannerisms of the writers he reads most frequently, a certain turn of phrase, a throw-away line, little nuances and subtleties that the not-so-heavy reader might not pick up on. I'm never quite certain whether that's a good thing or not - on the whole, though, anything that improves your standards has got to be good, hasn't it?
Buy a dictionary. Buy a Thesaurus as well. Carry that notepad around and jot your ideas down. Read, read, read - books, magazines, newspapers, anything that carries the printed word.
Songwriting, like any other musical discipline, isn't something that comes easily to most people - it has to be practised, polished and perfected. I haven't managed the third one yet, possibly I never will - but it won't be through lack of trying!
Good luck with the writing.....
Vic