The greeting sets the tone: “Dear Mr. Smith” (formal), “Hi John” (friendly) or “Hello team” (group). Avoid “Hey” in serious contexts.
In the body, get to the point: “I’m writing to…”, “I’d like to ask about…”, “Could you please…”. Short sentences work best.
The closing matters: “Best regards” and “Kind regards” are safe; “Cheers” is informal; “Looking forward to hearing from you” sounds proactive.