Here's some thoughts from the other Bert.

Shambles asks..
..why write songs? : Because you have something to say
..Are there not enough good ones around already? : No, just listen to the radio.
..Why not leave it to proper songwriters? : We are PROPER songwriters.

So Here's how I do it, for a ballad style song.

First decide what you want to say. What is the message you want to get across?
Decide on a punch line which sums up the message. That becomes your ending. If you haven't got an ending you haven't got a song.
The first verse has the job of getting the listener's attention.
Subsequent verses provide the build up to the last verse
The last verse delivers the message

For each verse you draw a picture in words. Make sure it is a real picture that you can see. Look at the covers on paperback novels, they do this quite well.
for each picture or verse, add some props. These should be real visual things. Things the listener can see in his/her mind.
Look at the comic pages in the newspapers. These guys are professionals at telling a story in just a few pictures.
Look at the props Bob Thaves uses in "Frank and Ernest"
That coffee urn really sets the scene for the greasy spoon cafe.

The props you use give you words which you can use for rhyming.

Let's look at a song you know. Here's the first line of "A song for a Winter's Night" by Gordon Lightfoot.

The lamp is burning low upon my table top.
OK. the song has nothing to do with lamps or tables, they are the props he uses to draw his picture. From this first line you know what time of day it is, it's late at night.
You know he is in some remote cabin because you don't use oil lamps in a downtown condo.
Next line.. The snow is softly falling.
See how he uses the snow as a prop to set the mood.
Next line...The air is still, in the silence of my room.
He is still using the picture of the room, and he is bringing the listener right in there with him.
Next line...I hear your voice sofltly calling.
Because he has set the stage so carefully you can almost hear her voice yourself.

Now you have got the hang of it, carry on songwriting.
I'll leave it to the musicians among us to talk about the tune.

Bert (the old one)