I find that music helps me. If I turn on iTunes on my computer, I'm less inclined to start pacing around the house or doing anything else on the computer that requires sound. It also helps me with the mood of a particular scene.

But I can't really force myself to concentrate on writing. My special interests go in a cycle, and if I'm concentrating on one of them then I barely pay attention to the other ones. Gaming? All Phoenix Wright, hardly any anime. Anime? That Wii won't be turned on for days. Writing? It's rare but when I get fired up I can do wonders.