I take no pride in the fact that I'm one of the biggest procrastinators around. So of course, it's no surprise that procrastination affects the writing aspect of my life as much as it does anything else - or at least, it used to. I've found ways to work around that and to be productive so that I never allow myself to slack off with my writing.
Here are a few things that have helped me:
1) Plan out how long you want to spend writing a manuscript. If it's within three months, figure out the minimum number of words you can do per day to reach that goal. E.g. 1000 words per day = 30,000 per month = 90,000 total. This gives you a concrete idea of the pace and helps you use your time wisely. Of course the numbers will vary day to day, but:
2) Always try to meet the goal you've set for yourself. Don't tell yourself "I'll make up for it tomorrow", because you might not feel like writing tomorrow either. Once you start putting things off, it will be all the more harder to get back up to speed.
3) If you're certain you can't meet your goal, write something. That way, you won't fall behind as much and you'll still keep up the habit. And if you're lucky, you might get into the writing mood while squeezing out what little you can, and reach your goal.
4) If you feel like exceeding your daily quota, do so. Self-explanatory.
5) Figure out what time of day works best for you. Some people like to write first thing in the morning, others have to wait until they get home at night. But by selecting a specific time to write each day, you make it easier for yourself to stay focused and not procrastinate.
6) Use external motivation as well as internal. We all want to see the fruits of our labor, but unfortunately, writing is normally solitary work. So the only one who will reward you will be you. Make the process more enjoyable for yourself with incentives. Or you could:
7) Create more immediate deadlines for yourself. If you have a critique partner, you can set up deadlines for one another (such as exchanging chapters twice a week).
8) Monitor your progress. Periodically calculate how far you've come along and how long it's taken you to get there. This not only helps you keep track of things, it can also give you an idea of whether your system works, or if it needs to be reworked.