If you freeze, thawing out again can be tough, so I have adopted a mechanical approach. I give myself some simple, time-restricted jobs, and I complete each one carefully, almost doltishly, with a constant awareness that it is real work and that it does serve the book. The best jobs for this are ones I can do in one or two hours, tops, and that have a definite beginning and end. Here are some examples of some good start-again tasks for the new chapter:
1. Make sure that I have accurate computer entries for every source I used in the just-handed-in chapter, plus photocopies of the title page and quoted pages for the file so I don't have to look it all up again if I lose my computer file.
2. Make sure I have a triple backup of the chapter. This means (a) e-mailing it to myself to put one on the server; and (b) e-mailing one to my mom, who never deletes anything. In addition to the computer file, these two extras are a little bit of insurance and they're pretty reliable.
3. Return all the library books that won't be needed for this new chapter, and check out the news ones that will. Organize them on the bookshelf, and mark appropriate chapters with Post-Its so I don't have to flip around while writing.
4. Re-read main sources for the chapter. This can be important! Sometimes I'm a few weeks or months from the last reading, and memories can fuzz. Re-reading is such an easy, relaxing prep for writing, and often it can be quite helpful.
5. Type out material that I know I intend to quote, and make sure an accurate citation is attached to it to avoid accidental plagiarism (a sin that is easier to do by mistake than you might think).
6. Use the Alastair Fowler writing method (discussed elsewhere in this blog) to brainstorm some ideas for the new chapter.
7. Write a teeny something, even if only a line or two, to get going again. This works rather like priming a pump.
Usually by this time I'm writing, but I confess that early first drafts generally feel stupid, unformed, confusing, and not very promising at all. That's okay. If I get stuck again I do another simple little task. If the writing is still going slowly, then sometimes I go out for coffee, bring a notebook, and commit to write one paragraph before leaving the cafe.
Oh, and by the way, I now have a proposal plus 75 manuscript pages. Some days I only wrote part of one page, and other days I wrote ten or more pages. Even on the part-of days, it adds up.