I love pieces like this one from the Guardian. Much of this applies whether you are writing fiction or non-fiction. Some highlights-- these are the pieces of advice I found utterly true and sometimes (or often) difficult:
Elmore Leonard: "My most important rule . . . if it sounds like writing, I rewrite it."
Margaret Atwood: "You most likely need a thesaurus, a rudimentary grammar book, and a grip on reality. This latter means: there's no free lunch. Writing is work. It's also gambling. You don't get a pension plan. Other people can help you a bit, but essentially you're on your own. Nobody is making you do this: you chose it, so don't whine."
Helen Dunmore: "Reread, rewrite, reread, rewrite. If it still doesn't work, throw it away. It's a nice feeling, and you don't want to be cluttered with the corpses of poems and stories which have everything in them except the life they need."
Anne Enright: "Only bad writers think that their work is really good."
Richard Ford: "Marry somebody you love and who thinks you being a writer's a good idea."
Jonathan Franzen: "The reader is a friend, not an adversary, not a spectator."
Esther Freud: "Editing is everything. Cut until you can cut no more. What is left often springs into life."
Neil Gaimon: "Remember: when people tell you something's wrong or doesn't work for them, they are almost always right. When they tell you exactly what they think is wrong and how to fix it, they are almost always wrong."
PD James: "Don't just plan to write – write. It is only by writing, not dreaming about it, that we develop our own style."
AL Kennedy: "Defend others. You can, of course, steal stories and attributes from family and friends, fill in filecards after lovemaking and so forth. It might be better to celebrate those you love – and love itself – by writing in such a way that everyone keeps their privacy and dignity intact."
More AL Kennedy: "Be without fear. This is impossible, but let the small fears drive your rewriting and set aside the large ones until they behave – then use them, maybe even write them. Too much fear and all you'll get is silence."
Everything Geoff Dyer says here is a gem, but I especially loved these: "Don't be one of those writers who sentence themselves to a lifetime of sucking up to Nabokov." Ha!
"Have regrets. They are fuel. On the page they flare into desire."
"Beware of clichés. Not just the clichés that Martin Amis is at war with. There are clichés of response as well as expression. There are clichés of observation and of thought – even of conception. Many novels, even quite a few adequately written ones, are clichés of form which conform to clichés of expectation."