"Entities must not be multiplied beyond necessity" (entia non sunt multiplicanda praeter necessitatem). Father William of Ockham (d'Okham) . (Entities=words, characters, motivations, dialog....I also call this the "need to know" principal--don't tell the reader any more than they actually NEED to know).
"When you get stuck, just blow something up." Andrew Cannon (This frequently works for me. I don't always blow up a thing--sometimes it's a relationship, sometimes a character's misconception, etc.)
"A novel is like a living body: everything has to connect to everything else. Anything that doesn't is a cancer, draining the vitality of everything around it. " Sean Williams
"Real people are damned inconvenient: they avoid issues, have oblique conversations, feel things others don't understand, and are very rarely think out loud in a coherent and rational way so that the protagonist can get important information." Kelley Eskridge
"The main advice is: Stop looking for advice and just keep putting words on paper. " Orson Scott Card
"Writer’s block is your friend. It is your unconscious mind telling you that something you just wrote, or are about to write, is not working....Your unconscious is your best editor – it tries desperately to keep you from writing crap. So the answer is NEVER to tough it out and force yourself to move on through your outline. The result of that will be garbage that you don’t care about and the reader won’t either." Orson Scott Card
"Fiddling with language or tiny meaningless details, of course, accomplishes nothing except to kill the spontaneity of the first draft. The first draft is the best draft – you only change spots where it isn’t clear or where the story isn’t working; you never just fiddle with language. That just kills your natural style....There is no virtue to eliminating “needless” words in fiction – and if you’re thinking about style, your style will be dead. You think about story and character, what happens and why, and let your natural voice carry the story. You’ll have an inimitable style then – your real voice – and the rules from the ignorant, miseducated English teachers who abused your understanding of the language throughout your miseducation will fall by the wayside, where they should be left behind. You can’t be thinking about language while you write; that’s like trying to ride a bicycle while thinking about balance and pedaling. And you’ve seen the stories that result from that kind of writing – a “style” that calls attention to itself constantly, so you can barely find the story through the English-professor-pleasing nonsense that has been smeared on the lens." Orson Scott Card