I have a lot of different ways for writing songs... lyrically who knows. Sometimes I can bang something out in a few minutes, other times I'll end up with 30 or 40 handwritten sheets of just crap. Not even lyrics, just ranting on something I'm angry, happy about, etc. I can go back to those later and highlight and pull out the stuff I really like that pops out or really says it the way I wanted too. I've got some good stuff that way. Sometimes all it takes is a catchy phrase, aliteration, or whatever. I quit trying to force myself to write a long time ago... anymore, I write whenever I have an idea. I had a 3 year dry spell on lyrics and didn't write anything, and then wrote about 9 full songs in one night, over the course of about 2 hours. I was in an interesting mood - I kept all but one of them. I also never throw anything away. I'll find stuff from 10 years ago that I forgot about, or that'll spark something else. Usually I try something different anymore.
On guitar... I do get in ruts. So I try alternate tunings. The last few times I tried new tunings I wrote about 4 songs almost immediately that I still think are good. Since I've had the home studio setup for about 2 months now, I've come up with a lot of ideas just arranging a simply drum track in Cubase from drum software and just speeding the tempo up, slowing it down, and just looping it and playing too it.
The methods I've gotten the best results out of usually only work once, though... I also try to keep up a lot on the news, politics, gossip, humanity in general. There is a neverending ammount of topic out there that I've pulled from, as most of my songs are about experiences that other people have had. My life is pretty good, and pretty boring so there isn't a lot of material there, I have to turn to the rest of the world....