But, five novels down, I've learned a few tricks...
1. Little and often is best. Even if there's only ten minutes available, grab it and write.
2. Anything you write can be made better, so it's worth writing rubbish.
3. If stuck, write description: what your character can see, hear, touch, feel, smell. Where are they? What are they wearing? How do they feel? What are they thinking? It's usually good for a couple of hundred words.
4. You often don't know what you're writing until you've written it. The act of writing unleashes all sorts of imaginative ideas and connections. Don't think, write.
Which is, of course, what I ought to be doing instead of blogging.