How To Professionally Write A Letter . Your mom was right—a good thank you letter makes you look like a champ! The first step before writing a letter is to identify the type of letter you are to be writing. FREE 6+ Professional Letter Format Samples in PDF MS Word from www.sampletemplates.com Here’s some insight into which of the above salutations you should choose from. Establish what you wish to accomplish when writing the letter. If you're using paper with a professional letterhead, you can skip this step.