Read three things you wrote and were proud of. A launch email, a long reply to a customer, a post that got real answers. You will notice the same habits in all three.
Those habits are your voice. Not "friendly" or "professional": those describe everyone. A voice is specific. You open with what happened. You use numbers instead of adjectives. You never end on a question.
Why it comes first
Every draft you approve later is checked against these rules. Without them, a draft can only be judged on whether it sounds fine, and fine is how every other company sounds.
What a good rule looks like
- It is something you could break. "Be clear" is not a rule. "One idea per paragraph" is.
- It quotes a sentence you actually wrote, so you can check it against your own work.
- It comes with the words you never use. Every writer has a list.