This staple of Strunk and White’s ELEMENTS OF STYLE is, perhaps, the best piece of advice I have to share.
But how do you know which words are unnecessary?
A quick and dirty way is to look for all of the thats. You can jettison most of them.
Then take a look at the fluff. Strike any copy if it:
* Doesn’t add anything substantial.
* Won’t change the work’s meaning or tone.
Remember: You’re writing for others as much as — if not more than — you’re writing for yourself.
If you’d skip over something, you better believe someone else will, too.
Choose a story you've written and revise it using this tip. Sorry, I've deleted my older drafts--next time I'll remember so I can post an example :)