I've been writing songs for about 6 years--just started spontaneously one day, although I suspect events at the time had a lot to do with it. I'd recently lost my dad, who taught me most of my traditional repertoire; and I was severely pissed-off over the so-called "Republican Revolution" of 1994. I started writing parodies, and it kind of mushroomed from there: I write anywhere from 15-30 songs a year and think I've gotten pretty good, at least as a lyricist. I tend to use mostly "folk-type" melodies, but that may be because I don't know much theory and it's easier for me to "KISS" where melody's concerned. I did a tape about 2 years ago and am getting started on a CD.
My philosophy on writing is that the more you do, the easier it gets. To put it a bit more "art-fully", the more you pursue the muse, the more she responds. (This is how we know the muse is female: a male muse would flee when pursued, right?) I used to set up specific writing times if I'd gone two weeks without anything coming spontaneously; now I give myself more of a break (I'll never get through my back catalogue anyway) but try to take advantage of natural opportunities. I write down ideas when I don't have time to work on them right away; and where I used to do housework when I had insomnia, now I pull out my "idea" folder and work on a song--a new idea, an unfinished piece, or an old piece I think could be improved.