If you don’t already own one, get yourself a copy of The Elements of Style by William Strunk, Jr. and E.B. White (of Charlotte’s Web fame)–a book that’s often referred to simply as “Strunk and White” by those who already know and love it.
Get it, and then read it. Cover to cover. You’ll find more good advice in there about grammar and how to write a strong, vigorous sentence than in all the creative writing workshops in the nation. Strunk and White stress clarity above all else, so grammar rules make sense–they’re only there to make writing a clear sentence that much easier.
Honestly, it’s a terrific little book, packed with useful information. And there’s a gorgeous recent edition illustrated by the brilliant Maira Kalman, if you want to give it as a gift or need pretty pictures to stay awake when you’re reading.
And while you’re acquiring books about writing, you might as well grab a copy of Stephen King’s On Writing, which is smart, practical, and inspiring. (His first novel really was rescued from the slush pile.)
I can’t think of any tools–other than my laptop, which is more like a child to me than a tool–seriously, I kissed it the other day–okay, that was weird, and I was doing it tongue in cheek, plus I’m very tired and not responsible for my actions–but the point is, I really do love it a lot and couldn’t live without it at this point–I mean, I could, but I don’t want to–
Where was I?–oh, right, I can’t think of any tools that have helped me more as a writer than these two books. I’m not a fan of reading about writing in general: as I said earlier, I think the best way to become a good writer is to read good books. But these are good books. Ones that just happen to be about writing.