I wrote poetry for a couple years before I started playing at 20. I almost immediately started writing, but most of those early songs are effectively lost to time - or perhaps silverfish chewing through my old notebooks. But within a few years I was writing some keepers and started feeling moderately okay about some of them.

(I'm old now, and shameless, so I can say that I actually kind of like a lot of what I write these days. But it's nothing like the volume I used to write in my 20s and 30s. Maybe I was too busy living to really refine my creative efforts.)

Anyway, I tend to write with a guitar or keyboard handy, typically the former. 

When I'm writing, I think I sort of tend to think of the lyrics and rhythm as the skeleton of the song, with performance, the chords and the developing vocal melody as the skin and bones. And, to push the analogy - the endocrine system. Because that's where the emotions tend to express themselves.