D is for Dissertation. It had to be Dissertation, though Diamonds or Dachshunds sounded more tempting...

Once you've headed down the road to doctoral distinction, the dissertation can begin to seem like everything: release from perpetual studenthood; proof that grad school was worth all the stress; something you can whip out to impress friends and neighbors (or use as a doorstop if you'd like to seem more nonchalant).
The dissertation is also the starting point for your career after graduate school.
There is so much good advice dissertation-writing done out there on the web already, or contained in books you can have downloaded or overnighted by Amazon; it hardly makes sense to mention how getting up and writing 20 minutes every morning can make all the difference, or how it's important to understand your own writing process and motivations, or why you should conceive of the dissertation, from the start, as a publishable product (a series of journal articles, or an 80,000 word book, depending on your field).
So I thought I'd offer two small pieces of advice, as one PhD to another very-nearly-one. They're two things I'd go back in time and tell my own self if I could, one near the very end of the process, and right at the start.
If you're near end, and it's starting to seem like an intolerable slog-that is to say, you're really beginning to doubt you'll be able to see this through-then there's only one thing you need to hear: go find someone who knows how to knock the rest of this project down to size and walk you through the final steps.
The letter "D" in your case has to stand for Don't be proud--or Don't hesitate to reach out for help.
The process fails many people at exactly the point you've reached. Profs are excited to move on to grads who are just getting started. Almost no departments have staff in place to help grads who are dissertating. You're at the point where many people most need hands-on mentorship, but where everyone wants you to pretend you know exactly what you're doing from here on out.
So you're going to have to be insistent and creative. Start with your committee members-tell them one by one you know you can finish but right now you don't see the game plan. Ask them for concrete guidance as to what each next step should look like. Ask them if there's a way you can pull back on the scope of the diss-perhaps defer one part of the analysis until after you've finished, then make that the subject of your first post-dissertation journal article?
If none of your committee members is able to help you see a clear path to the finish line, then move on. Go to profs who aren't on your committee but who you know take mentoring seriously. Consider whether there's a secretary in your department who quietly helps nudge dissertators to the finish line. (The woman behind the Turabian system of citation was herself a secretary at the University of Chicago-you've got to wonder how many grads she helped across the three decades she worked there.)
Or seek out grads who have recently finished. Or grads who are also writing now, and whose working style you appreciate; find out if they'd be interested in buddying up.
And if none of this helps-or if you'd just rather start with a different option to begin with--start exploring the many links you'll find right here on this site. Some academic editing services offer far more than editing. Some will read your roughest chapter drafts and help you figure out how to whip them into shape. Some even offer coaching services for dissertators.
You may not love the idea of paying for support you expected your department to provide-but then again sometimes an objective outsider who understands the process can make all the difference in the world. (Good luck, and May the force be with you!)
If, on the other hand, you're just starting out, just beginning to shape a topic or write the dissertation proposal, then there's one very crucial thing you need to do now that few people are willing to suggest. That is: think very honestly about your MO as a graduate student, and shape your proposal proactively to counter the ways you tend to get bogged down.
For instance, are you that grad who's always reaching for big and bold ideas, projects that could have an impact your field-but also someone who spent all your vacations and summers of graduate school struggling to finish incompletes? Then this is the moment to get real and consider how hard it is to reconfigure a dissertation once it's out of control.
Think. Small.
Shape a topic that matters to you but is far less ambitious than you ever imagined you'd find adequate for your diss. Have no doubt-it will expand in the course of your work, and it will take more work than you ever imagined. But it will be doable, and doable is what counts most now. The most brilliant project in the world won't mean much if it winds up sitting in a drawer somewhere, unfinished.
Or maybe, just the opposite, you're the kind of grad who has always played it safe? Churned out research papers that never strayed far into new territory, but were practical and fairly painless to complete?
Let me just say: your caution is a beautiful thing. It makes you someone who is likely to get the dissertation done-not to mention someone who is likely to start publishing soon after you move on.
But now is a good time to remember that your dissertation research will be your calling card. If you play it too safe, you may well find it hard to get anyone excited about your work. You may find it hard to get yourself excited too-and when you're nearing the end of the process, you may well need to be able to remember something about this project that excited you in the beginning.
No one's saying that now is the time to reach for the moon and the stars. But please do make sure there's one component to your project that takes a little risk, lets you ask a question you're pretty sure you don't know the answer to. Don't just see this as a chance to get a dissertation done-try to see it as a chance to grow as a scholar; to tackle at least one little problem it will be cool to talk about at your job interviews; to write something you can believe in.