Select nice stationery with a matching envelope. Although it is not strictly required, your note will look both more elegant and more personal on pretty paper than on lined notebook sheets. You can order expensive embossed stationery or simply choose something you like at an office supply store.

Open with a friendly greeting, making sure that you spell your daughter-in-law’s name correctly. Refer to her however you normally do, whether it is Joanna or Jo-Jo. Avoid the tendency to become stiff or formal.

Say “thank you,” and specify what you are thanking her for. Use the first sentence to create the context for the letter, such as thanking your daughter-in-law for a recent favor or explaining what she means to you.

Add details, but avoid rambling. If your daughter-in-law gave you a gift, tell her how you plan to use it. If the letter is an expression of gratitude for your relationship, describe three or four specific ways in which she enhances your life.

Show off your personality and individual flair. A letter of thanks is an intimate exchange between two people, not a rigid business correspondence. Feel free to use casual language, idioms, slang and references to in-jokes or past experiences that the two of you shared.

Mention a future get-together. Whether she has dinner at your house once a week or will visit sometime next year, tell your daughter-in-law how much you are looking forward to seeing her again. Personalize this connection by noting something specific that you really enjoy about her, such as her shrimp cocktail or talent on the golf course.

Close the letter with another reference to your thanks along with a detail or two that you did not mention previously.

Sign off with a warm farewell. Instead of “Sincerely,” try “Missing You,” “Love,” “Warmly,” or another expression that highlights your relationship.