A friend of mine once told me "There's no such thing as writer's block, just poor planning." I've found it true in many cases. When I get stuck, I try to think of where I want my story to go, then decide what the best way to get there is. Then I write, even if it's bad, if I can get through the section that's giving me trouble it's worth it. You can always go back and fix it later.

The other thing I do is I make myself a playlist to listen to with songs that I think suit the characters or scenes I'm writing. I listen to it when I write but also when I'm stuck in traffic and trying to think up scenes for the story.