This is a interesting topic. I have heard good guitarists on different guitars and amps and the cool thing is they sound the same. My conclusion is it does not matter what you play, it matters how you play. As far as out board effects go I've been using a Peavey Profex II, and a BBE Sonic Maximizer. With the Peavey I don't use much effects, I mainly use just a little bit of delay, and a bit of pitch just to fatten things up a little.
Every song has it's own entity, so they all start out differently.
I'll build chords and rhythms around it. Most of my songs start on the guitar, but a few have been composed on the keyboard. It also helps to have a good producer. If one of them strikes me as a cool idea I'll attempt to complete it. Home studios and commercial studios are becoming one of the same.