Really. Nothing is lost by cutting ‘really’ from the sentence but simplicity and function is gained. There’s also the issue of considering what the word “real” means. Real is a fact, it is not imagined. When you take this into consideration you’ll find that using really as an intensifier often conveys more emotion than we intended. If you are going to use this word, make sure to do so sparingly as to not lessen its impact.
Things/Stuff. While the writer may have a perfectly clear understanding of what ‘things’ and ‘stuff’ they are referring to, the burden is placed on the reader to figure out what the writer is talking about. Instead, define.
I believe/I Feel/I think. Instead of the focus being on the subject, it is on the author. You don’t need to say ‘I believe’ we already know it’s what you believe, you’re the one writing it.
Was/Is/Are/Am. (Passive voice: “The letter was mailed by Sally.” Active voice: “Sally mailed the letter.”) Passive voice is most often used in scientific writing, and that’s usually where it belongs. It tends to be less engaging and requires the writer to use more words per sentence. Passive voice forces the reader to do more work to get to the same conclusion. Active voice allows for short, punctuated sentences that get to the point.
Very. “Substitute ‘damn’ every time you’re inclined to write ‘very’; your editor will delete it and the writing will be just as it should be.” — Mark Twain.  The word ‘very’ does not communicate enough information. It’s been called one of the most useless words in the English language. It’s one of those penny words that writers throw in to magnify another word. The only problem is, it doesn’t do that. Instead of saying, “very good” say “wonderful.” Another solution is to cut the word ‘very’ out of the sentence completely.