Do not omit a word or phrase necessary to the meaning of the sentence.
--From the Harbrace College Handbook
This sentence, which sets a new world record for obviousness, appeared in a 1986 school textbook on writing.
And they say kids today are poorly educated.
My advice is the exact opposite. Bias your writing towards the omission of more words. Try taking away words and see if your writing is clearer. Most likely it will be. And after one pass of word omission, make another pass and omit still more words. You'll usually find your sentences clearer still--and even more forceful.
And don't worry about eliminating words necessary to the meaning of the sentence, a specious worry if there ever was one. It will be painfully obvious if the meaning of one of your sentences is affected after omitting a few words, and you can easily put those words back.
Direct and economical language communicates best. Make life easy for your readers. We're not here to bury them in words, we're here to help them understand.