I’m a big proponent of starting songs from distinct “seeds”—fragments of lyric, melody, rhythm, or just strong ideas for songs. This approach is pretty much the unspoken “go to” technique pro writers use to jumpstart their writing process on a regular, even daily basis. I describe a more intentional and disciplined approach to the practice in the first chapter of my new book, Songwriting Strategies: A 360º Approach.
One of the best sources I know for lyric seeds in particular is reading. One nice perk in catching seeds from reading: You flake out on the couch all afternoon reading your latest young adult, SF or mystery guilty pleasure. When you find a good phrase on page 237, you can say to yourself, in virtuous, only slightly defensive tones: “Well, actually I’ve been working all afternoon. This is research!” (Your spouse may not buy the argument.)
Recently I was reading a cool new book— The Incrementalists, by Steven Brust and Skyler White—that combines a bit of time travel (my favorite) with a bit of Dan Brown-ish secret society thriller, along with quite a droll tone. In one bit of dialogue, a main character says something like, “I was never good at good, I always believed in better…” That was my seed.
The Songwriter's Compass 