When you write something: a book, an article, an email... cut out needless words. The copy after editing should be shorter. Writing is not speaking, it must be tighter. (And, if you find an email is getting longer, just phone the person, he'll never read the email anyway)
I've read somewhere Mark Twain was saying that "very" should always be cut out. I started paying attention to my use of "very" and found that a sentence only wins after I un-very it.
Today I came across this article listing 5 more words to cut out. So here's the list of no-no words, should make any editing process much easier:
Check the comments too, there was an interesting insight about words we use to "temper" our speech which we should probably omit when writing, words such as "slightly", "a bit", "somewhat".
And here's another excellent piece on editing I just found:
there is no good writing, only good re-writing