Some of this feels original to me but that's just not true.
- Set a daily minimum for time spent written
- Set a weekly minimum for words written
- Keep editing and rewrites to a minimum until the first draft is completed
- Rewrite and then submit for publication
- Never end a writing session at the end of a scene. If the scene has ended, start a new one before getting up. If the story is finished, start a new story.
That last point is one of the best pieces of advice for me, and I so wish I knew where I heard it first. It has made sitting down and working... not easy, but much easier.