Bread and Butter Letters

The logic of “bread and butter letter,” a term first appearing in print in the US in the early 20th century... The writer is thanking his or her hosts for their hospitality (and food), but the letter is also a basic social formality, not likely to contain any exciting content. A “bread and butter” note may not be eagerly awaited, but it’s the sort of thing expected and probably noticed most in its absence.
- Word Detective

The "bread and butter letter," might be an old-fashioned term but it is one an important concept for a mannered life: Writing a thank you note for hospitality.
Except in the case of immediate family dinners and events, if one has had a meal, an overnight, a weekend, or any other form of generosity bestowed upon them in another's home, a bread and butter letter should always arrive to the host/ess promptly. There is an urban-hostess legend that circulates about one Type-A hostess who carries her thank you notes, with the envelope stamped, in her car. So that she does not forget the details of the evening or weekend, she writes her note immediately and drops it in her mailbox on the way into her house. This process appeals to me though I find it a dangerous step beyond my own compulsiveness.
If it works for you though, I admire your process.

Ultimately, you need to get the note out right away. Assuming you brought or bestowed a hostess gift, it should only be a note. If you went empty-handed, now is your chance to get something in the mail to redeem yourself (it need not be costly: An enlarged photo from your visit with us alone would be forever cherished in my realm as I would guess, in all.)

And you need to write the note, regardless of your penmanship, in your own hand, and put it in the mail. That is just as important because it indicates you went to some trouble. An email is not sufficient.

A few notes then on what this note should include:

1. Date. Salutation.

2. Initially, advise the address/addresses that your note is one of thanks for yourself and anyone else who attended with you from your household:

"Dear Marissa.
A note of many thanks for this past weekend in Malibu. The gift of your time and friendship is always precious to me. And your picturesque home the perfect antidote to my wintry, compressed New York. I am so glad to catch up and I feel like a new person. I am so very grateful..."

3. Always include details in thank-you notes:
"The views were amazing. I cannot believe I was lucky enough to awake in that setting. It was paradise..."

If there was additional generosities, remember to include those also:
"Dinner at Nobu was incredible. I am still star-struck from being seated next to Mena Suvari."

If she or he has paid attention to every detail on the guests behalf, do not allow their effort to go unmentioned:
"The sheets were cool and calming and smelled like jasmine, what a thoughtful touch."

4. Always remark on, and specifically use the word, "generosity."
"I was spoiled by your generosity."

5. Whatever you write, keep the tone light and pleasant.