All writer's hit writer's block to some degree or other. Here's what I learned through the process of writing my first book:
1. There are rhythms to writing. Sometimes the writing flows, other times it doesn't. Its important to accept this. But when it does flow go with it - write as much as you can. Other times I couldn't mentally face writing the next chapter so I would see what I could face doing. Sometimes I wouldn't be in a chapter-writing mood but I would be up for researching a later chapter so I went with that. I had to watch that I wasn't avoiding writing completely, but having a strict deadline from my publisher helped motivate me.
2. Structure, structure, structure. I experimented by 'winging' some chapters. I tried start writing the chapter to see what happened. The experiment failed and it took me a lot longer to write the chapters I did this experiment with than the ones that I had planned out in detail. Interesting I hit writer's block the least the more structure I was with planning my chapters.
3. Don't write until you feel good emotionally about your chapter (or book) plan. If something doesn't sit well with you work out what it is and then try and solve it before you start writing. This vastly reduces the risk of hitting writer's block.