I've never had any desire to write lyrics (or poems, or stories) but some of the song Challenge topics that have been presented are too interesting to pass up. So I made a couple attempts at writing songs, which has raised a couple questions for me.

When I start writing a song, basically I have a few ideas and/or rhymes, but have to really work at getting the sentences(?) put together so that the rhythm and accents are correct. I write a line or verse, go back and change a couple words, possibly add a syllable, re-read it and sing it out loud, and maybe scrap it and start again. Is this common, or do most of you just have the songs flow right out of your mind on the first attempt?

How long should a song be? The longer I worked on the last topic (devils inside the computers) the more ideas I kept getting. I could have kept writing on and on, adding themes and expanding ideas, but at 1am I decided to go to bed (since I had to be up at five). How do I know when to stop writing?

Is song writing supposed to be akin to writing a composition in English class, i.e. should there be a topic sentence/introduction, supporting paragraphs, and summary/conclusion? This is the approach I've taken on the songs I've done so far. Are there other pieces that should go in also?

Keeping in mind that I don't plan on ever doing "serious" songwriting, e.g. record an album, perform, or be published, I would appreciate input from anyone who would like to answer my questions or express their opinion on their own style of songwriting.