As of 2009, there were 21.9 million military veterans living in the United States, according to the U.S. Census Bureau. Although Veterans Day is set aside to honor the nation's soldiers, many civilians look for other ways to express their appreciation. If you're interested in writing a letter to a veteran, there are a few tips to help you accomplish the task.

Identify a veteran. If you know a veteran through work, church or some other organization, obtain his name and address. If you don't know a specific veteran, contact your state's Department of Veteran Affairs and ask for procedures on how to send a letter of gratitude to a veteran. You can also go online to research organizations such as Operation Gratitude (opgratitude.com) that have a list of veterans to whom they send letters.

Practice writing the letter several times, jotting down what you want to say. Keep the letter positive and thank the veteran for his service to the country and how that service made you feel as an American. Write the final letter using your practice letter as reference. Sign and date the letter.

Proofread your letter for spelling errors and for clarity. If you made a mistake, rewrite the letter until there are no errors. Include your name and address in the body of the letter to personalize what you've written.

Confirm the address where you are sending the letter and write it on the front of the envelope. Double check to ensure that you've written the correct address. Include your return address on the top left of the envelope.

Mail the letter and choose certified mail or delivery confirmation service at the post office.