Write a handwritten letter. A handwritten letter is more thoughtful and personal than a typed letter that could be created by a mail merge computer program. It's also more sufficient to convey your thoughts than a pre-printed greeting card. The time and effort you put into writing a handwritten letter will show.

List your thoughts you want to include in the letter. A list of thoughts will help you plan for how much space your text will occupy in the letter so you can adjust the size of your handwriting accordingly.

Personalize the letter. Address the couple jointly and personally. The opening sentence sets the tone and theme of the letter. Express your happiness on the engagement or how excited you were when you receive the wedding invitation card. Share your feelings as warmly as the occasion warrants. The final sentence or paragraph concludes with your best wishes for the couple's future together. Avoid using a valediction that is too impersonal. Don't write anything that would sour the occasion. Now is not the time to reveal any hidden romantic feelings or convince them not to get married.

Mail the letter to the recipient. There's something exciting about receiving a letter in the mail. Make sure to include your return address on the envelope in case the letter proves undeliverable for whatever reason. Use a postage stamp instead of a postage meter stamp to make the envelope more personalized. Mail the letter as soon as possible so the recipients have time to read it before the wedding.