I haven't got a degree in literature (or, indeed, anything at all) or an MA in Creative Writing, or a library of books on Structure and Three Act Plot-building.
All I can tell you is what works for me. Here goes.
1) Set yourself targets. For When I Was Joe I aimed for a thousand words a day, or 5-6,000 a week. This forces you to write, even when you think you're writing rubbish. And create a final deadline for your first draft.
2) The aim at the beginning is to get to know the people you are writing about. If you're not sure how the story is going to develop just write something from the main character's past or future.
3) Don't be a snob. I think many people are put off even trying to write because they think they have to be a literary genius, crafting deep and poetic prose. Actually they're often better off writing the very best crime novel or romantic comedy that they can. Free youself from the tyranny of trying to win the Booker prize.
4) 'Write what you know' does not mean that you are stuck with your boring (or interesting) autobiography masquerading as fiction. Think of an interesting idea, sketch out a vague plot and then draw on your own experience to make the events and emotions you describe as real as possible. And don't be scared of asking other people about their experiences.
5) Some people plan everything first, work out their plot and have intricate wall charts and chapter plans. Others just plunge in with a vague outline. That's fine. I think of plot planning as a bit like a cruise. You need to know the beginning and the end destination, and have a few fixed points to aim at, but the rest is an adventure, subject to change.
6) If in doubt, tell yourself: it's only a first draft. Everything can be changed. This works right up to the final edits.
7) Writing believable dialogue - listen to people's conversations. Write them down word for word. Try and catch the rhythm of different ways of speaking.
8)Write a book that you'd enjoy reading. If you don't fall in love with your own story, how can you expect a reader to?
9)If you're writing about a postman in Cumbria, don't torture yourself worrying that he's unrepresentative of real Cumbrian postmen. He's an individual. You can build his story to make him plausible.
10) Examine every sentence to eliminate unnecessary words. There's always something that can be cut.