Writer's block? What's that? :) .... Seriously, when I get stuck, I find a way to push through being stuck, because I am paid to write and I need to meet my deadlines. Some of my "tricks" to get unstuck:
1) re-read what I've written to see why I'm having a problem with the current scene. Most of the time I see a problem earlier that I can fix, which helps me move forward.
2) skip the scene I'm stuck in and write the next scene that I can picture. Often, the scene where I'm stuck doesn't need to be written at all.
3) edit what I have so far to help me get back into the story.
4) take a break -- whether 30 minutes on the treadmill, an hour watching television, or even a run to the grocery store -- sometimes taking a breather helps breathe life into the story when I return. Taking a break can also mean a night out with friends, taking the kids to a movie, or playing board games.
5) play the "what if" game -- run through a variety of scenarios to see what feels right.
6) Don't be afraid to slash and burn -- meaning, cut whole scenes that don't work or completely rewrite sections if that's what it takes to move forward.