Let me disqualify myself from the outset and say that I am no expert on writer's block except to the extent that I've experienced it and have learned to deal with it.
I think it might be useful for me to share with you what works for me to get past the block and refocus on writing.
For me, it comes down to two things: 1) distraction, and 2) positioning.
I don't think any of you will be surprised by the first point. I seem to have varying levels of difficulty writing when there are distractions in the background, whether it is the TV, music, friends talking, or even just my own mind worrying about some chore on my list.
What I've found works in addressing this first point is turning all of the distractions off. I know it sounds obvious, but if you've been there, you know that it can be hard to do. When I turn everything off (including the music that I sometimes mistakenly thinks helps me write), sit in silence and review my outline, the ability to write returns. In our world of ever-increasing distraction opportunities, you have to create your silence as best you can, there's no way around it.
My second strategy is a bit strange, but I've heard other writers have similar habits. I've noticed that if I write in the same spot for a few hours or a few days, my ability to write seems to go flat, and this staleness is easily corrected by switching positions. It is often as simple as shifting over to the other side of the couch or getting up and sitting on the opposite side of the table.
These two simple steps, together, get me past all of the block that I experience. The hardest part is the discipline to turn all the distractions off.
There are a few more intricacies on this subject and I think I might share some more on it in the future, but for now...back to writing!