Hello, I am writing a letter to an ACA(O) that i have never dealt with, yet alone met. I figured it would be a good idea to try and get the letter writing ettiquette right, first impressions etc. Any tips, or the correct way to go about this would be greatly appreciated. Addressed to: Col. (Retd). Joe Bloggs MC Thanks. P.S. I am aware that Dear Sir/ Yours Sincerely will probably suffice, but if there were any blindingly obvious things to include etc.