More on that from Amazon, Austrailian Government, a blogger, Economist, Elements of Style(1920), Columbia University, and Distributed Proofreader's wiki.
For word choice try: Power Thesaurus, lose the "very", Careful Words, and Linking Words.
After The Deadline has proofreading tips&tricks
Ask a friend or teacher for help.
Computers (spellchecking software) at the problem: