Writer's block is definitely one of the most frustrating things I run into in life! Usually I will wait a little while - perhaps a day or two - and see if it clears. Many times that works. I also switch up what I am writing; I will change from the project I am on and start writing songs or poems. Another thing that I have found helpful is to look at other artistic or inspirational things - the things that would inspire me to write in the first place - and see if they spark anything. I have also taken the more visceral approach and written about writer's block itself as if I am challenging my nemesis! That is satisfying.