Beginning and ending:
1. Dear Sir or Madam, Yours faithfully
2. Dear Mr. Smith, Yours sincerely
First sentences, stating the purpose of the letter:
I am writing with regard to
I am writing to request/ to ask for
I am writing to thank you for
I am writing to inform you that
I am writing to inform you of my decision to
I am writing to complain about
I am writing to bring to your attention
On behalf of all of my colleagues, I would like to thank you for
Thank you for your help and support.
I look forward to receiving your response.
I await your prompt response.
I hope that you will address these concerns as soon as possible. ( Complaint )
Please let me know if you require any further information.
I hope that my request does not cause you any inconvenience.
Three tips:
Avoid contractions: " I am " instead of "I'm"
Avoid direct questions: "I would like" instead of "Can I have?"
Avoid exclamation marks "!"