Grappling With Writer’s ... Um ...

Plow on through
The most common strategy is just to start writing and push through the mental barrier that’s blocking you. In this case, it doesn’t matter what you write, just write it. You can go back and edit later. Chances are you’ll find yourself on a roll within a couple of minutes.

I also find it helpful to occasionally walk away from the computer and do it “old school” style by getting a pen and paper and just writing longhand. I often find that while writing on a computer, I edit my work as I go along instead of concentrating on the idea I’m writing about. Writing by hand breaks you out of that habit.