Writer's block is that awkward moment when you neither give up nor can do something you want to do because reasons. It's a mysterious moment in life of anyone who ever tried to do something. Writers usually suffer from it much more substantially than the others thus the informal title.
In short - writer's block is something of a friend who overstays his welcome. It's been a good time to have a little pause, a moment of calmness and now you need to make a segue and start working - but no, you can't. Sometimes you hype yourself up too much towards certain project and at the certain moment - you're unable to because you're afraid to fail to live up to expectation. That's where Writer's Block kicks in with a purposeful grimace and a terrible vacuous presence.
Some say that it is the form of procrastination. That's not correct. Procrastination is when you're doing something instead of what you need to do, thus postponing the end result with possibly catastrophic consequences.
Writer's block is a full stop. You just sit at your desk, stare at the screen or sheet of paper and have no idea what to do. It's perplexing and petrifying. And utterly irritating. You feel empty. No thoughts - no words. It can go as far as deleting the material you already have assembled - because it's not as good as it needs to be.
Writer's Block is one unpredictable bastard. There's no universal recipe on how to battle it. Although, about ten years ago one of my professors said that the best way to fight writer's block is to "take it easy". If only he could clarify what he meant under "taking it easy". Anyway, here's a few tips that might help to ease the suffering or even overcome our ill-beloved bloke called Writer's Block.
ACKNOWLEDGE THE PROBLEM
Writer's block is not something that you can prevent. You can't even foresee its coming. It just happens and have to admit that you have an issue. After that you need to start dealing with it. If not - good luck then. Hope your eyesight will not fail you after a while. Understanding the source of the problem is the crucial part of fixing it. Think about the reasons of having The Block - what stopped you? Don't say "everything". It's probably not true. Is it the general idea that is somewhat lacking and off-putting? Or you're not sure how to express it? Or you have troubles with structuring the whole thing?
Sometimes the block kicks in because you're not ready to start - you've made not enough research and your overall plan is a bit vague and rather ambiguous. In such case you just need to go back and do more research. That might help. If not - do it again until it works.
ROCK AROUND THE BLOCK
Exactly. When you understand your problem it becomes far less imposing. You know its shape and its position. And so you can maneuver yourself around it. You need to understand what you can do in your situation. You can do it by sketching various parts of the text, noting some important details to be incorporated in the text at a later stage and then combining it by putting the meat on the bones of notes and sketches.
EVOKE A BRAINSTORM
YEAH! Brainstorm is Writer's Block worst enemy. Brainstorm just comes a shoots that damn bloke in the face. And you don't even notice it. Nothing does it better. Brainstorming on a certain subject can eliminate Writer's Block with such extreme prejudice that in retrospect you may consider that act a war crime. But it's not just a Brainstorm that kills the Writer's Block - it's a Brainstorm of utterly poor ideas. Why bother brainstorming something intentionally bad? Because it is easier.
Since The Block is standing against any creative movement, especially a positive one - imagine what will happen to the fella if there's will be a whole lotta negative whirls going on around - intentionally terrible thoughts, lacking expressions, horrendous imagery - you can almost hear Block screaming "AAAAAAAARRRRRGGGGGHHHHHHH!".
Writer's block can't stand that torture and after a while - negative brainstorm transforms into a positive one and you can start working again. However sometimes because of intense negativity you just deepen your inability to work. But there's a trick to avoid it. The so-called Alan Coren method. In short it is - skip the first and second ideas and go straight to the third (or further).
NEVER MIND THE DISTRACTIVE DOUBTS
AKA "another useful tip that says nothing substantial". Writer's block has one very powerful collaborator inside you. And his name is "Inner Editor" - the one who points out minor issues (that will be fixed in the second draft anyway) while you're deep in the flow writing like hell. He takes you out because you're not attentive to the comas and continuity or some other thing. He also puts Distractive Doubts in you. Since you can't keep up with the correct use of comas - how dare you to write? While he's reasonable (to put it kindly), he actually helps to install the reign of terror by Writer's block. He's turned on you. Kill him mercilessly. Since Inner Editor is not a living person - you can resurrect him later.
Even keeping the other tips in mind - remember - Writer's Block is unpredictable and ruthless dissident aggressor. He brings inaction on the grounds of vanity and shatters your rock solid motivation with the Hammer of the High Hopes. Don't let him to do it. If no other tip will help you - here something I consider an ace in the hole.
Pretend The Block is some jacked guy in a pink ballet costume - laugh at him. Laugh hard - as hard as you can. Writer's block doesn't like to be laughed at. He considers it as an insult. And in riposte he will turn its non-existent back and walk away offended. Even if this tip is just a syrupy wishful thinking - it worked for me once. And I actually heard The Block slamming the door.
As you can see - Writer's block is like flu. If you don't take action on it - it will kill. But if you will - it's a joke.