We've all had it - that moment when you sit down to write and the words just won't seem to come out onto the paper. There can be a number of reasons for this. Sometimes you've got a plot hole that needs fixing before you can progress. Sometimes You're tired - it's hard to be creative when you're exhausted. Sometimes you're just stressing too much about it. There are other causes too - and the best solution is to work out why you have block and deal with that.
My personal solutions to writer's block:
1. If the problem is with the plot I'll work out what I need to do to fix it and make notes but not rewrite it at this point. Then I'll carry on as if I'd already made the changes. This can make the first draft a bit confusing to anyone who isn't you - but this is why I don't show people my first drafts (well that and the fact they're awful)
2. If I'm tired I do the obvious and get some sleep. I get some of my best inspiration from dreams anyway and lack of sleep isn't healthy.
3. If I'm stressing I do something distracting - in my case that usually involves reading, listening to music, or some combination of the two.
4. Write something else. If I really can't work on the project I had in mind I'll write something else instead. Sometimes leaving a project for a few days. This can be good with plot problems because it can take a few days to be ready to analyse the problem
5. Take a bath - always good for stress.
6. Go somewhere else to write. I've mentioned this one before - it really works for me. Get out of the house go to a coffee shop, the park or anywhere you like where you can sit and write. A change of scene can really help.
And here are some other people's tips. There will probably be some duplication here as other people have found the same tricks.