Ask professional writers to describe effective writing and they'll give you more answers than you need.
That might suggest that they don't agree on what makes writing effective. But they do agree. They just use different language to describe what they do and like to read.
For several years, I've been a chair of international judging panels for a business writing competition. We judges have different cultural and technical backgrounds, but our differences of opinion are around our overall impressions as we give different weightings to the qualities and imperfections of particular entries.
We can sum up what professional writers do in just these six ideas. I've taught them to thousands of writers in New Zealand, Australia, Hong Kong and Singapore.
1. Focus on the reader. It's the golden rule of writing.
2. Keep it simple - fewer words, simple sentences as building blocks. (But don't hesitate to use more words if they will improve your reader's understanding, or your rapport.)
3. Write informally - not casually, but with informality appropriate to a conversation with that reader on that topic.
4. Be direct. Tell them your key point early - even if it's the second sentence in your email. Say what you really mean, with appropriate diplomacy.
5. Use the active voice, unless there's a good reason to use passive.
6. Make it 'personal'. Think of it as the opposite of impersonal, rather than necessarily I or me. Any humans will make your writing personal. Impersonal writing is dry and doesn't make it clear who is involved.
Think of the combination of those ideas as a writing and editing method, not just some tips. They are all you need to turn professional as a business writer.