Question: How do I learn to write something with which I am unfamiliar?
Answer: Here's a book for your writing library: How To Write It: A Complete Guide to Everything You'll Ever Write. Sandra E Lamb. Berkeley/Toronto: Ten Speed Press. 1998, 2006.
The title pretty well sums up the purpose of this book. Each chapter comes with a somewhat wordy introduction that I, at least, simply skimmed right over. Instead, I went directly to the model letters, announcements, memos and other types of writing. These models make several points clear:
1. State the facts and purpose of your writing clearly, completely and succinctly. Don't waste time. Get to the point immediately.
2. Supply necessary details.
3. Finish with a gracious ending.
Notice of divorce. 1. State that you and your spouse are divorcing, preceded by "Regrettably."
2. Temporary addresses for each.
3. Appreciate your friendship and will be in touch.
Notice of new employee: 1. Name and position
3. Drop by and introduce yourself.
Obituary. 1. Name, date and place of death
2. Spouse (if applicable)
3. Birth date. Names of parents.
5. Other survivors.
Notice of meeting. 1. Purpose. Date. Location. Time--beginning and end.
2. Breakfast/lunch if applicable
3. Agenda attached or will arrive by date.
4. RSVP by specified date.
Sympathy. 1. Saddened to learn
2. Good memories
3. Express our sympathy to....
You understand the idea. Facts up front. Necessary details. Gracious ending.
Good resource if you do not know how to begin writing a particular type of message. Should help you at least to start. You can add variations as needed.
Includes models of cover letters for employment, resumes, letters of complaint, etc.