Where is your favorite place or setting to write music? I like to write in the dark because it helps me focus on the music more, so I sit in front of my amp and only use the light from my green amp jewel.
you're never as free as when you are lost
That sounds like a good place...I write really anywhere, but being in a quiet, relaxing place tends to be easier, like in my room, etc...
When I sit down to write specifically, I just sit down at my desk and write. It's big enough that I can spread out my scraps of paper, my regular notebooks and my small pocked notebook as well, and a writer's thesaurus and my laptop.

Most often though I end up just writing whatever comes to mind wherever I happen to be.
I find that I prefer to do initial writing in solitude (at home) and re-writing/editing at a coffee shop.
Polishing, I do by running the song on a different instrument. Ex: if I wrote it on the guitar, I check it on the piano, and vice-versa, checking to make sure my chord progression doesn't sound too lame. Hope this helps.