Omit needless words.

I could have stated this advice as Omit unnecessary words, but that may not say to you exactly what I mean. I could have said Omit superfluous words, but superfluous is a big word and just vague enough to be interpreted as "Leave out any word you can." So I chose to state this guideline exactly as Professor William Strunk Jr. did nearly a century ago in The Elements of Style: Omit needless words:

Vigorous writing is concise. A sentence should contain no unnecessary words, a paragraph no unnecessary sentences, for the same reason that a drawing should have no unnecessary lines and a machine no unnecessary parts. This requires not that the writer make all sentences short, or avoid all detail and treat subjects only in outline, but that every word tell.

When an editor says something you wrote is "wordy," that just means you could have used fewer words to say the same thing. It might mean that you used two words where one would do. So, don't take it personally: it doesn't mean that your writing is wooly or verbose.

Expert writers go through their work multiple times, scrutinizing every sentence, looking for better ways to say what they mean and looking for ways to say the same thing in fewer words.

Why? Because look at all the words there are on a page. That's a lot of information to process. Anything extraneous contributes to "fog." It makes writing harder to process on the fly. You are selling a product, so make it reader friendly.