"Writer's block" is, for me, a sign that I need to take a break. Sometimes the answer is to do some gardening or other manual work, and let the subconscious get on with formulating the next bit of writing. A bit of non-verbal recreation can go a long way towards getting me back on track.
However, at times, the problem is simply a lack of inspiration. I'm plugging away at a piece, pounding out my thoughts on the keyboard, and suddenly I draw a blank. I simply have no words to chuck into the space that I've opened up there on the page. Sometimes I actually run right over the edge into empty space, and, like Wiley Coyote, it takes me a moment to realize that there's nothing beneath my feet.
So I back up, make a note of where I was in the thought process, and go in search of some inspiration. And what constitutes inspiration? For me, the best place to go is into a book by one of my favorite authors: Loren Eisely, A. J. Heschel, J.R.R. Tolkien....
I don't need to read the whole book, I just need to drink in the flavor of their imagery, a taste of their sense for scenery and emotion. Usually, just a few pages is enough to get me back on track. The words that I needed to fill in that hole in my prose will be there waiting for me when next I sit down at the keyboard. Inspiration is always only a bookshelf away.