Well, I am wary of writing rules, but they are usually right. The Guardian published this article a few days ago featuring some of today's well-known writers and their top ten rules on writing. While some are obvious -- read a lot, write a lot, don't use adverbs, avoid prologues, etc, it's interesting to hear these rules in the words of the writers themselves. The article is chock-full of good advice. Some of my favorites:
"The two most depressing words in the English language are 'literary fiction'." -David Hare
"Interesting verbs are seldom very interesting." -Jonathan Franzen
"Do keep a thesaurus, but in the shed at the back of the garden or behind the fridge, somewhere that demands travel or effort." -Roddy Doyle
"Only bad writers think that their work is really good." -Anne Enright
And so forth. Read the whole thing here.