Set a word count goal. My minimum goal is 7 pages per week, which comes to about 2450 words.
Give yourself permission to write poorly. You are the worst judge of your own writing, especially in a first draft. You need to get around your hangups if you want to be productive. The only way to do this is to stop caring what the world will think.
Meditate. I do it for 15-20 minutes before I start. I close my eyes, pay attention to my breathing, and still my mind. You can’t focus if you have a head full of burning spiders.
Nevertalk about what you’re currently writing. Talk about what you’ve already written if you must. Ideally, unless you need to be flogging your “platform” and self-promoting, don’t talk about your writing at all. Put it out there and let others talk about how great or horrible you are.
Always talk about the craft of writing but only after you’ve done your writing for the day.
Program yourself by creating rituals and routines that inform your body and mind it’s time to write. I try to write at the same time every day. After I meditate, I have coffee, light a little incense (which replaced a cigarette years ago), and disconnect from electronic media.
Always end with something more left to say in the scene. It will take far more energy tomorrow to start from zero than in media res.
Do not compare yourself to other writers, ever. You are a unique snowflake. Believe it.
Avoiding low blood sugar is one of the secret keys to intellectual productivity, especially for creative people. Have your donut, but be sure to also snack on fruit and seeds.
After you write and dump all your energy into your work, do a little exercise to avoid feeling exhausted for hours. I currently do yoga and chi gong, but a good swim or a jog would be just as effective, I think.