The Guardian has published a few thoughts from people who really ought to know about how to write.
I’m not sure they are rules, as such. More like guidelines:

‘The two most depressing words in the English language are “literary fiction”.’
– David Hare

‘Only bad writers think that their work is really good.’
– Anne Enright

‘Finish the day’s writing when you still want to continue.’
– Helen Dunmore

‘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.’
– Margaret Atwood

‘Never use a verb other than “said” to carry dialogue.’
-Elmore Leonard

You can read it all here.
I’m going back to my desk to deal with a few sloppy verbs.