Know your grammar. If you don’t, check it. Buy yourself a grammar book, dictionary and thesaurus, and use them. If you don’t, copy-editing will be a long, painful and costly process. Better to get it right yourself in the first place.
And if you’d like to tweet a link to THIS post, here’s my suggested tweet:
Writers’ BLOCKbusters: know your grammar http://wp.me/p5gEM4-1ut #writingtips via @SandraDanby