For me, it's usually a particular sound that gets me going. I'll be fiddling around with the pedal and come up with one of the presets and start practicing. From there, just noodling, I'll stumble upon a riff that will sound good as a beginning, or a lead in to a chorus. Once I have a chorus, the verses just seem to fall into place, along with a vocal melody.
Song lyrics, on the other hand, are a whole 'nuther story. I can usually come up with a catchy chorus, but for some reason, my verses sound cheesy to me. Either their oversimplified, or just waaaaaaaay too complicated.
Thank God for my other guitar player. He's great at coming up with direct, simple phrases that make sense.
I like to collaborate anyway. It's more fun writing with a group for me.
Guitars:
Fender 2006 MIM Fender Stratocaster HSS in 3TS
Ibanez RG 570 with a bridge Invader
ESP M II Deluxe with a Tune-o-Matic bridge
Eleanor, the magical, mystical Road Worn wonder Tele
Blackstar HT Club 40